21157817604 has 288 divisors, whose sum is σ = 64865525760. Its totient is φ = 5304499200.

The previous prime is 21157817581. The next prime is 21157817617. The reversal of 21157817604 is 40671875112.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 24015244 + ... + 24016124.

It is an arithmetic number, because the mean of its divisors is an integer number (225227520).

Almost surely, 2^21157817604 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 21157817604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32432762880).

21157817604 is an abundant number, since it is smaller than the sum of its proper divisors (43707708156).

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

21157817604 is a wasteful number, since it uses less digits than its factorization.

21157817604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1039 (or 1030 counting only the distinct ones).

The product of its (nonzero) digits is 94080, while the sum is 42.

The spelling of 21157817604 in words is "twenty-one billion, one hundred fifty-seven million, eight hundred seventeen thousand, six hundred four".