21959815680 has 360 divisors, whose sum is σ = 83606078556. Its totient is φ = 5322915840.

The previous prime is 21959815673. The next prime is 21959815699. The reversal of 21959815680 is 8651895912.

21959815680 is a `hidden beast` number, since 21 + 9 + 59 + 8 + 1 + 568 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 20474175744 + 1485639936 = 143088^2 + 38544^2 .

It is a tau number, because it is divible by the number of its divisors (360).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 2783902 + ... + 2791778.

Almost surely, 2^21959815680 is an apocalyptic number.

21959815680 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 21959815680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41803039278).

21959815680 is an abundant number, since it is smaller than the sum of its proper divisors (61646262876).

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

21959815680 is a wasteful number, since it uses less digits than its factorization.

21959815680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7928 (or 7898 counting only the distinct ones).

The product of its (nonzero) digits is 1555200, while the sum is 54.

The spelling of 21959815680 in words is "twenty-one billion, nine hundred fifty-nine million, eight hundred fifteen thousand, six hundred eighty".