21137988 has 24 divisors (see below), whose sum is σ = 49477792. Its totient is φ = 7023744.

The previous prime is 21137981. The next prime is 21137999. The reversal of 21137988 is 88973112.

It is not an unprimeable number, because it can be changed into a prime (21137981) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1431 + ... + 6657.

Almost surely, 2^21137988 is an apocalyptic number.

It is an amenable number.

21137988 is an abundant number, since it is smaller than the sum of its proper divisors (28339804).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21137988 is a wasteful number, since it uses less digits than its factorization.

21137988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5571 (or 5569 counting only the distinct ones).

The product of its digits is 24192, while the sum is 39.

The square root of 21137988 is about 4597.6067687439. The cubic root of 21137988 is about 276.4953821168.

It can be divided in two parts, 2113 and 7988, that added together give a palindrome (10101).

The spelling of 21137988 in words is "twenty-one million, one hundred thirty-seven thousand, nine hundred eighty-eight".