21666353652165 has 8 divisors (see below), whose sum is σ = 34666165843488. Its totient is φ = 11555388614480.

The previous prime is 21666353652157. The next prime is 21666353652179. The reversal of 21666353652165 is 56125635366612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21666353652165 - 2³ = 21666353652157 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 722211788391 + ... + 722211788420.

It is an arithmetic number, because the mean of its divisors is an integer number (4333270730436).

Almost surely, 2^{21666353652165} is an apocalyptic number.

It is an amenable number.

21666353652165 is a deficient number, since it is larger than the sum of its proper divisors (12999812191323).

21666353652165 is a wasteful number, since it uses less digits than its factorization.

21666353652165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1444423576819.

The product of its digits is 34992000, while the sum is 57.

The spelling of 21666353652165 in words is "twenty-one trillion, six hundred sixty-six billion, three hundred fifty-three million, six hundred fifty-two thousand, one hundred sixty-five".