21231660645 has 96 divisors (see below), whose sum is σ = 40687920000. Its totient is φ = 10177546752.

The previous prime is 21231660623. The next prime is 21231660661. The reversal of 21231660645 is 54606613212.

21231660645 is a `hidden beast` number, since 2 + 1 + 2 + 3 + 1 + 6 + 6 + 0 + 645 = 666.

It is not a de Polignac number, because 21231660645 - 2⁷ = 21231660517 is a prime.

It is a congruent number.

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 95 ways as a sum of consecutive naturals, for example, 3690231 + ... + 3695979.

It is an arithmetic number, because the mean of its divisors is an integer number (423832500).

Almost surely, 2^21231660645 is an apocalyptic number.

It is an amenable number.

21231660645 is a deficient number, since it is larger than the sum of its proper divisors (19456259355).

21231660645 is a wasteful number, since it uses less digits than its factorization.

21231660645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5939 (or 5936 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The spelling of 21231660645 in words is "twenty-one billion, two hundred thirty-one million, six hundred sixty thousand, six hundred forty-five".