21364779520 has 320 divisors, whose sum is σ = 62224588800. Its totient is φ = 6872186880.

The previous prime is 21364779517. The next prime is 21364779533. The reversal of 21364779520 is 2597746312.

It is a tau number, because it is divible by the number of its divisors (320).

It is a super-2 number, since 2×21364779520² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 44602641 + ... + 44603119.

It is an arithmetic number, because the mean of its divisors is an integer number (194451840).

Almost surely, 2^21364779520 is an apocalyptic number.

21364779520 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 21364779520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31112294400).

21364779520 is an abundant number, since it is smaller than the sum of its proper divisors (40859809280).

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

21364779520 is a wasteful number, since it uses less digits than its factorization.

21364779520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 659 (or 643 counting only the distinct ones).

The product of its (nonzero) digits is 635040, while the sum is 46.

The spelling of 21364779520 in words is "twenty-one billion, three hundred sixty-four million, seven hundred seventy-nine thousand, five hundred twenty".