21917915712 has 392 divisors, whose sum is σ = 81314373312. Its totient is φ = 5692032000.

The previous prime is 21917915699. The next prime is 21917915759. The reversal of 21917915712 is 21751971912.

21917915712 is a `hidden beast` number, since 2 + 1 + 9 + 1 + 79 + 1 + 571 + 2 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 3589462 + ... + 3595562.

Almost surely, 2^21917915712 is an apocalyptic number.

21917915712 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21917915712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40657186656).

21917915712 is an abundant number, since it is smaller than the sum of its proper divisors (59396457600).

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

21917915712 is an equidigital number, since it uses as much as digits as its factorization.

21917915712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6149 (or 6124 counting only the distinct ones).

The product of its digits is 79380, while the sum is 45.

The spelling of 21917915712 in words is "twenty-one billion, nine hundred seventeen million, nine hundred fifteen thousand, seven hundred twelve".