21621808 has 20 divisors (see below), whose sum is σ = 45115168. Its totient is φ = 9979200.

The previous prime is 21621793. The next prime is 21621823. The reversal of 21621808 is 80812612.

It is an interprime number because it is at equal distance from previous prime (21621793) and next prime (21621823).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51768 + ... + 52183.

Almost surely, 2^21621808 is an apocalyptic number.

It is an amenable number.

21621808 is an abundant number, since it is smaller than the sum of its proper divisors (23493360).

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

21621808 is a wasteful number, since it uses less digits than its factorization.

21621808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103972 (or 103966 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21621808 is about 4649.9255908025. The cubic root of 21621808 is about 278.5890242040.

The spelling of 21621808 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred eight".