21612637872 has 120 divisors (see below), whose sum is σ = 69291691040. Its totient is φ = 6160250880.

The previous prime is 21612637867. The next prime is 21612637901. The reversal of 21612637872 is 27873621612.

21612637872 is a `hidden beast` number, since 2 + 1 + 6 + 1 + 2 + 637 + 8 + 7 + 2 = 666.

It is a super-2 number, since 2×21612637872² (a number of 21 digits) contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 398904 + ... + 449832.

Almost surely, 2^21612637872 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21612637872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34645845520).

21612637872 is an abundant number, since it is smaller than the sum of its proper divisors (47679053168).

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

21612637872 is a wasteful number, since it uses less digits than its factorization.

21612637872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51371 (or 51362 counting only the distinct ones).

The product of its digits is 338688, while the sum is 45.

The spelling of 21612637872 in words is "twenty-one billion, six hundred twelve million, six hundred thirty-seven thousand, eight hundred seventy-two".