21216726520 has 64 divisors (see below), whose sum is σ = 52854768000. Its totient is φ = 7600010880.

The previous prime is 21216726437. The next prime is 21216726539. The reversal of 21216726520 is 2562761212.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 330370 + ... + 389329.

It is an arithmetic number, because the mean of its divisors is an integer number (825855750).

Almost surely, 2^21216726520 is an apocalyptic number.

21216726520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21216726520 is an abundant number, since it is smaller than the sum of its proper divisors (31638041480).

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

21216726520 is a wasteful number, since it uses less digits than its factorization.

21216726520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 719788 (or 719784 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 34.

The spelling of 21216726520 in words is "twenty-one billion, two hundred sixteen million, seven hundred twenty-six thousand, five hundred twenty".