21891064520 has 64 divisors (see below), whose sum is σ = 53093214720. Its totient is φ = 8075314944.

The previous prime is 21891064511. The next prime is 21891064579. The reversal of 21891064520 is 2546019812.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 554477 + ... + 592643.

It is an arithmetic number, because the mean of its divisors is an integer number (829581480).

Almost surely, 2^21891064520 is an apocalyptic number.

21891064520 is a gapful number since it is divisible by the number (20) 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 21891064520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26546607360).

21891064520 is an abundant number, since it is smaller than the sum of its proper divisors (31202150200).

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

21891064520 is a wasteful number, since it uses less digits than its factorization.

21891064520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39294 (or 39290 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 38.

The spelling of 21891064520 in words is "twenty-one billion, eight hundred ninety-one million, sixty-four thousand, five hundred twenty".