21660353656353 has 12 divisors (see below), whose sum is σ = 31287302968740. Its totient is φ = 14440177863936.

The previous prime is 21660353656349. The next prime is 21660353656369. The reversal of 21660353656353 is 35365635306612.

21660353656353 is a `hidden beast` number, since 2 + 1 + 6 + 6 + 0 + 3 + 536 + 56 + 3 + 53 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 2139924271104 + 19520429385249 = 1462848^2 + 4418193^2 .

It is not a de Polignac number, because 21660353656353 - 2² = 21660353656349 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21660353656353.

It is not an unprimeable number, because it can be changed into a prime (21660353656343) 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, 2391976 + ... + 7003017.

It is an arithmetic number, because the mean of its divisors is an integer number (2607275247395).

Almost surely, 2^{21660353656353} is an apocalyptic number.

It is an amenable number.

21660353656353 is a deficient number, since it is larger than the sum of its proper divisors (9626949312387).

21660353656353 is a wasteful number, since it uses less digits than its factorization.

21660353656353 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9651168 (or 9651165 counting only the distinct ones).

The product of its (nonzero) digits is 26244000, while the sum is 54.

The spelling of 21660353656353 in words is "twenty-one trillion, six hundred sixty billion, three hundred fifty-three million, six hundred fifty-six thousand, three hundred fifty-three".