21660745673566 has 4 divisors (see below), whose sum is σ = 32491118510352. Its totient is φ = 10830372836782.

The previous prime is 21660745673561. The next prime is 21660745673569. The reversal of 21660745673566 is 66537654706612.

It is a semiprime because it is the product of two primes.

It is a junction number, because it is equal to n+sod(n) for n = 21660745673498 and 21660745673507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21660745673561) by changing a digit.

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 as a sum of consecutive naturals, namely, 5415186418390 + ... + 5415186418393.

It is an arithmetic number, because the mean of its divisors is an integer number (8122779627588).

Almost surely, 2^{21660745673566} is an apocalyptic number.

21660745673566 is a deficient number, since it is larger than the sum of its proper divisors (10830372836786).

21660745673566 is a wasteful number, since it uses less digits than its factorization.

21660745673566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10830372836785.

The product of its (nonzero) digits is 228614400, while the sum is 64.

The spelling of 21660745673566 in words is "twenty-one trillion, six hundred sixty billion, seven hundred forty-five million, six hundred seventy-three thousand, five hundred sixty-six".