21813907680 has 144 divisors (see below), whose sum is σ = 78818869584. Its totient is φ = 5474856960.

The previous prime is 21813907679. The next prime is 21813907711. The reversal of 21813907680 is 8670931812.

21813907680 is a `hidden beast` number, since 2 + 181 + 390 + 7 + 6 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 421066 + ... + 470025.

It is an arithmetic number, because the mean of its divisors is an integer number (547353261).

Almost surely, 2^21813907680 is an apocalyptic number.

21813907680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21813907680 is an abundant number, since it is smaller than the sum of its proper divisors (57004961904).

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

21813907680 is a wasteful number, since it uses less digits than its factorization.

21813907680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 891129 (or 891118 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The spelling of 21813907680 in words is "twenty-one billion, eight hundred thirteen million, nine hundred seven thousand, six hundred eighty".