21645374472864 has 60 divisors (see below), whose sum is σ = 63658445071914. Its totient is φ = 7215124823424.

The previous prime is 21645374472857. The next prime is 21645374472877. The reversal of 21645374472864 is 46827447354612.

21645374472864 is a `hidden beast` number, since 2 + 1 + 64 + 53 + 7 + 447 + 2 + 86 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 17851808019600 + 3793566453264 = 4225140^2 + 1947708^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 4175416867 + ... + 4175422050.

Almost surely, 2^{21645374472864} is an apocalyptic number.

21645374472864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21645374472864 is an abundant number, since it is smaller than the sum of its proper divisors (42013070599050).

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

21645374472864 is an equidigital number, since it uses as much as digits as its factorization.

21645374472864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8350838939 (or 8350838922 counting only the distinct ones).

The product of its digits is 216760320, while the sum is 63.

The spelling of 21645374472864 in words is "twenty-one trillion, six hundred forty-five billion, three hundred seventy-four million, four hundred seventy-two thousand, eight hundred sixty-four".