21106781579520 has 3888 divisors, whose sum is σ = 98163187654896. Its totient is φ = 4146934579200.

The previous prime is 21106781579503. The next prime is 21106781579537. The reversal of 21106781579520 is 2597518760112.

21106781579520 is a `hidden beast` number, since 2 + 1 + 1 + 0 + 67 + 8 + 1 + 57 + 9 + 520 = 666.

It is an interprime number because it is at equal distance from previous prime (21106781579503) and next prime (21106781579537).

It can be written as a sum of positive squares in 8 ways, for example, as 5108829513984 + 15997952065536 = 2260272^2 + 3999744^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 431 ways as a sum of consecutive naturals, for example, 289133994204 + ... + 289133994276.

Almost surely, 2^{21106781579520} is an apocalyptic number.

21106781579520 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 21106781579520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49081593827448).

21106781579520 is an abundant number, since it is smaller than the sum of its proper divisors (77056406075376).

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

21106781579520 is a wasteful number, since it uses less digits than its factorization.

21106781579520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 230 (or 175 counting only the distinct ones).

The product of its (nonzero) digits is 2116800, while the sum is 54.

The spelling of 21106781579520 in words is "twenty-one trillion, one hundred six billion, seven hundred eighty-one million, five hundred seventy-nine thousand, five hundred twenty".