21538788 has 24 divisors (see below), whose sum is σ = 50356992. Its totient is φ = 7165344.

The previous prime is 21538757. The next prime is 21538789. The reversal of 21538788 is 88783512.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21538789) 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, 5806 + ... + 8762.

It is an arithmetic number, because the mean of its divisors is an integer number (2098208).

Almost surely, 2^21538788 is an apocalyptic number.

It is an amenable number.

21538788 is an abundant number, since it is smaller than the sum of its proper divisors (28818204).

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

21538788 is a wasteful number, since it uses less digits than its factorization.

21538788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3571 (or 3569 counting only the distinct ones).

The product of its digits is 107520, while the sum is 42.

The square root of 21538788 is about 4640.9899805968. The cubic root of 21538788 is about 278.2320061759.

The spelling of 21538788 in words is "twenty-one million, five hundred thirty-eight thousand, seven hundred eighty-eight".