21817860346872 has 256 divisors, whose sum is σ = 65240456486400. Its totient is φ = 6730718976000.

The previous prime is 21817860346859. The next prime is 21817860346901. The reversal of 21817860346872 is 27864306871812.

It is a happy number.

21817860346872 is a `hidden beast` number, since 2 + 1 + 8 + 17 + 8 + 603 + 4 + 6 + 8 + 7 + 2 = 666.

It is a congruent number.

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, 943218747 + ... + 943241877.

It is an arithmetic number, because the mean of its divisors is an integer number (254845533150).

Almost surely, 2^{21817860346872} 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 21817860346872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32620228243200).

21817860346872 is an abundant number, since it is smaller than the sum of its proper divisors (43422596139528).

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

21817860346872 is a wasteful number, since it uses less digits than its factorization.

21817860346872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27435 (or 27425 counting only the distinct ones).

The product of its (nonzero) digits is 43352064, while the sum is 63.

The spelling of 21817860346872 in words is "twenty-one trillion, eight hundred seventeen billion, eight hundred sixty million, three hundred forty-six thousand, eight hundred seventy-two".