21620538 has 12 divisors (see below), whose sum is σ = 46844538. Its totient is φ = 7206840.

The previous prime is 21620531. The next prime is 21620561. The reversal of 21620538 is 83502612.

21620538 is a `hidden beast` number, since 2 + 1 + 620 + 5 + 38 = 666.

21620538 is nontrivially palindromic in base 14.

It can be written as a sum of positive squares in only one way, i.e., 11716929 + 9903609 = 3423^2 + 3147^2 .

It is not an unprimeable number, because it can be changed into a prime (21620531) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 600553 + ... + 600588.

Almost surely, 2^21620538 is an apocalyptic number.

21620538 is an abundant number, since it is smaller than the sum of its proper divisors (25224000).

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

21620538 is a wasteful number, since it uses less digits than its factorization.

21620538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1201149 (or 1201146 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21620538 is about 4649.7890274721. The cubic root of 21620538 is about 278.5835696033.

The spelling of 21620538 in words is "twenty-one million, six hundred twenty thousand, five hundred thirty-eight".