1987 (number)

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← 19861987 1988 →
Cardinal one thousand nine hundred eighty-seven
Ordinal 1987th
(one thousand nine hundred eighty-seventh)
Factorization prime
Prime 300th
Greek numeral ,ΑϠΠΖ´
Roman numeral MCMLXXXVII
Binary 111110000112
Ternary 22011213
Senary 131116
Octal 37038
Duodecimal 119712
Hexadecimal 7C316

1987 is the natural number following 1986 and preceding 1988.

Contents

In mathematics

1987 is an odd number and the 300th prime number. It is the first number of a sexy prime triplet (1987, 1993, 1999). Being of the form 4n + 3, it is a Gaussian prime. It is a lucky number and therefore also a lucky prime. 1987 is a prime factor of the 9th number in Sylvester's sequence, and is the 15th prime to divide any number in the sequence.

There are 1987 polyiamonds with 12 cells that tile the plane isohedrally. [1]

In other fields

Related Research Articles

In number theory, a lucky number is a natural number in a set which is generated by a certain "sieve". This sieve is similar to the sieve of Eratosthenes that generates the primes, but it eliminates numbers based on their position in the remaining set, instead of their value.

15 (fifteen) is the natural number following 14 and preceding 16.

17 (seventeen) is the natural number following 16 and preceding 18. It is a prime number.

79 (seventy-nine) is the natural number following 78 and preceding 80.

31 (thirty-one) is the natural number following 30 and preceding 32. It is a prime number.

37 (thirty-seven) is the natural number following 36 and preceding 38.

67 (sixty-seven) is the natural number following 66 and preceding 68. It is an odd number.

93 (ninety-three) is the natural number following 92 and preceding 94.

1000 or one thousand is the natural number following 999 and preceding 1001. In most English-speaking countries, it can be written with or without a comma or sometimes a period separating the thousands digit: 1,000.

300 is the natural number following 299 and preceding 301.

500 is the natural number following 499 and preceding 501.

700 is the natural number following 699 and preceding 701.

600 is the natural number following 599 and preceding 601.

800 is the natural number following 799 and preceding 801.

900 is the natural number following 899 and preceding 901. It is the square of 30 and the sum of Euler's totient function for the first 54 positive integers. In base 10, it is a Harshad number. It is also the first number to be the square of a sphenic number.

163 is the natural number following 162 and preceding 164.

777 is the natural number following 776 and preceding 778. The number 777 is significant in numerous religious and political contexts.

223 is the natural number following 222 and preceding 224.

277 is the natural number following 276 and preceding 278.

Euler's "lucky" numbers are positive integers n such that for all integers k with 1 ≤ k < n, the polynomial k2 − k + n produces a prime number.

References

  1. ↑ (sequence A075223 in the OEIS ).
  2. ↑ (sequence A061997 in the OEIS ).


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