21665594500 has 72 divisors (see below), whose sum is σ = 52010463960. Its totient is φ = 7878376000.

The previous prime is 21665594491. The next prime is 21665594513. The reversal of 21665594500 is 549556612.

It can be written as a sum of positive squares in 4 ways, for example, as 145878084 + 21519716416 = 12078^2 + 146696^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 118555 + ... + 239554.

It is an arithmetic number, because the mean of its divisors is an integer number (722367555).

Almost surely, 2^21665594500 is an apocalyptic number.

21665594500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21665594500 is an abundant number, since it is smaller than the sum of its proper divisors (30344869460).

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

21665594500 is a wasteful number, since it uses less digits than its factorization.

21665594500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 358150 (or 358127 counting only the distinct ones).

The product of its (nonzero) digits is 324000, while the sum is 43.

The spelling of 21665594500 in words is "twenty-one billion, six hundred sixty-five million, five hundred ninety-four thousand, five hundred".