21604957 has 16 divisors (see below), whose sum is σ = 24998400. Its totient is φ = 18465840.

The previous prime is 21604949. The next prime is 21604967. The reversal of 21604957 is 75940612.

It is a cyclic number.

It is not a de Polignac number, because 21604957 - 2³ = 21604949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34594 + ... + 35212.

It is an arithmetic number, because the mean of its divisors is an integer number (1562400).

Almost surely, 2^21604957 is an apocalyptic number.

It is an amenable number.

21604957 is a deficient number, since it is larger than the sum of its proper divisors (3393443).

21604957 is a wasteful number, since it uses less digits than its factorization.

21604957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 816.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21604957 is about 4648.1132731464. The cubic root of 21604957 is about 278.5166324205.

It can be divided in two parts, 2160 and 4957, that added together give a palindrome (7117).

The spelling of 21604957 in words is "twenty-one million, six hundred four thousand, nine hundred fifty-seven".