21081518136 has 160 divisors (see below), whose sum is σ = 68861100000. Its totient is φ = 6023227392.

The previous prime is 21081518113. The next prime is 21081518147. The reversal of 21081518136 is 63181518012.

21081518136 is a `hidden beast` number, since 2 + 1 + 0 + 8 + 1 + 518 + 136 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21081518136.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 174840 + ... + 269688.

It is an arithmetic number, because the mean of its divisors is an integer number (430381875).

Almost surely, 2^21081518136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21081518136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34430550000).

21081518136 is an abundant number, since it is smaller than the sum of its proper divisors (47779581864).

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

21081518136 is an equidigital number, since it uses as much as digits as its factorization.

21081518136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94888 (or 94861 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The spelling of 21081518136 in words is "twenty-one billion, eighty-one million, five hundred eighteen thousand, one hundred thirty-six".