21506662737665 has 16 divisors (see below), whose sum is σ = 29556427668480. Its totient is φ = 14716637920320.

The previous prime is 21506662737647. The next prime is 21506662737697. The reversal of 21506662737665 is 56673726660512.

It is not a de Polignac number, because 21506662737665 - 2²⁶ = 21506595628801 is a prime.

It is a super-2 number, since 2×21506662737665² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21506662737598 and 21506662737607.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 641398766 + ... + 641432295.

It is an arithmetic number, because the mean of its divisors is an integer number (1847276729280).

Almost surely, 2^{21506662737665} is an apocalyptic number.

It is an amenable number.

21506662737665 is a deficient number, since it is larger than the sum of its proper divisors (8049764930815).

21506662737665 is a wasteful number, since it uses less digits than its factorization.

21506662737665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1282831552.

The product of its (nonzero) digits is 114307200, while the sum is 62.

The spelling of 21506662737665 in words is "twenty-one trillion, five hundred six billion, six hundred sixty-two million, seven hundred thirty-seven thousand, six hundred sixty-five".