21121579567956 has 144 divisors (see below), whose sum is σ = 60397656164160. Its totient is φ = 5712355353600.

The previous prime is 21121579567919. The next prime is 21121579567967. The reversal of 21121579567956 is 65976597512112.

It is a super-2 number, since 2×21121579567956² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12630486 + ... + 14204658.

Almost surely, 2^{21121579567956} 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 21121579567956, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30198828082080).

21121579567956 is an abundant number, since it is smaller than the sum of its proper divisors (39276076596204).

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

21121579567956 is a wasteful number, since it uses less digits than its factorization.

21121579567956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1575414 (or 1575405 counting only the distinct ones).

The product of its digits is 71442000, while the sum is 66.

The spelling of 21121579567956 in words is "twenty-one trillion, one hundred twenty-one billion, five hundred seventy-nine million, five hundred sixty-seven thousand, nine hundred fifty-six".