21813925209444 has 81 divisors (see below), whose sum is σ = 55389441455257. Its totient is φ = 7238661342528.

The previous prime is 21813925209421. The next prime is 21813925209469. The reversal of 21813925209444 is 44490252931812.

The square root of 21813925209444 is 4670538.

It is a perfect power (a square), and thus also a powerful number.

21813925209444 is a `hidden beast` number, since 2 + 1 + 8 + 1 + 392 + 5 + 209 + 4 + 44 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18692738720100 + 3121186489344 = 4323510^2 + 1766688^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 6697549864 + ... + 6697553120.

Almost surely, 2^{21813925209444} is an apocalyptic number.

21813925209444 is the 4670538-th square number.

It is an amenable number.

21813925209444 is an abundant number, since it is smaller than the sum of its proper divisors (33575516245813).

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

21813925209444 is an frugal number, since it uses more digits than its factorization.

21813925209444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7002 (or 3501 counting only the distinct ones).

The product of its (nonzero) digits is 4976640, while the sum is 54.

The spelling of 21813925209444 in words is "twenty-one trillion, eight hundred thirteen billion, nine hundred twenty-five million, two hundred nine thousand, four hundred forty-four".