21018900502656 has 768 divisors, whose sum is σ = 71573089985280. Its totient is φ = 5796790272000.

The previous prime is 21018900502643. The next prime is 21018900502777. The reversal of 21018900502656 is 65620500981012.

21018900502656 is a `hidden beast` number, since 2 + 1 + 0 + 1 + 8 + 90 + 0 + 502 + 6 + 56 = 666.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 19998953331 + ... + 19998954381.

It is an arithmetic number, because the mean of its divisors is an integer number (93194127585).

Almost surely, 2^{21018900502656} 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 21018900502656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35786544992640).

21018900502656 is an abundant number, since it is smaller than the sum of its proper divisors (50554189482624).

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

21018900502656 is a wasteful number, since it uses less digits than its factorization.

21018900502656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1845 (or 1830 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 45.

The spelling of 21018900502656 in words is "twenty-one trillion, eighteen billion, nine hundred million, five hundred two thousand, six hundred fifty-six".