21057813504 has 792 divisors, whose sum is σ = 81034965648. Its totient is φ = 5202247680.

The previous prime is 21057813493. The next prime is 21057813509. The reversal of 21057813504 is 40531875012.

21057813504 is a `hidden beast` number, since 21 + 0 + 57 + 81 + 3 + 504 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21057813509) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 99799959 + ... + 99800169.

Almost surely, 2^21057813504 is an apocalyptic number.

21057813504 is a gapful number since it is divisible by the number (24) 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 21057813504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40517482824).

21057813504 is an abundant number, since it is smaller than the sum of its proper divisors (59977152144).

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

21057813504 is a wasteful number, since it uses less digits than its factorization.

21057813504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281 (or 253 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The spelling of 21057813504 in words is "twenty-one billion, fifty-seven million, eight hundred thirteen thousand, five hundred four".