21660615072 has 72 divisors (see below), whose sum is σ = 61791948036. Its totient is φ = 7197398016.

The previous prime is 21660615061. The next prime is 21660615077. The reversal of 21660615072 is 27051606612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20142421776 + 1518193296 = 141924^2 + 38964^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is not an unprimeable number, because it can be changed into a prime (21660615077) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27333 + ... + 209924.

Almost surely, 2^21660615072 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 21660615072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30895974018).

21660615072 is an abundant number, since it is smaller than the sum of its proper divisors (40131332964).

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

21660615072 is a wasteful number, since it uses less digits than its factorization.

21660615072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 237590 (or 237579 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The spelling of 21660615072 in words is "twenty-one billion, six hundred sixty million, six hundred fifteen thousand, seventy-two".