21555020120520 has 256 divisors, whose sum is σ = 68174353728000. Its totient is φ = 5443703422976.

The previous prime is 21555020120509. The next prime is 21555020120533. The reversal of 21555020120520 is 2502102055512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 862982272 + ... + 863007248.

It is an arithmetic number, because the mean of its divisors is an integer number (266306069250).

Almost surely, 2^{21555020120520} is an apocalyptic number.

21555020120520 is a gapful number since it is divisible by the number (20) 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 21555020120520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34087176864000).

21555020120520 is an abundant number, since it is smaller than the sum of its proper divisors (46619333607480).

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

21555020120520 is a wasteful number, since it uses less digits than its factorization.

21555020120520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29752 (or 29748 counting only the distinct ones).

The product of its (nonzero) digits is 10000, while the sum is 30.

The spelling of 21555020120520 in words is "twenty-one trillion, five hundred fifty-five billion, twenty million, one hundred twenty thousand, five hundred twenty".