15 (fifteen) is the natural number following 14 and preceding 16.
21 (twenty-one) is the natural number following 20 and preceding 22.
29 (twenty-nine) is the natural number following 28 and preceding 30. It is a prime number.
37 (thirty-seven) is the natural number following 36 and preceding 38.
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.
400 is the natural number following 399 and preceding 401.
127 is the natural number following 126 and preceding 128. It is also a prime number.
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.
2000 is a natural number following 1999 and preceding 2001.
10,000 is the natural number following 9,999 and preceding 10,001.
131 is the natural number following 130 and preceding 132.
167 is the natural number following 166 and preceding 168.
181 is the natural number following 180 and preceding 182.
20,000 is the natural number that comes after 19,999 and before 20,001.
30,000 is the natural number that comes after 29,999 and before 30,001.
