21660165266 has 4 divisors (see below), whose sum is σ = 32490247902. Its totient is φ = 10830082632.

The previous prime is 21660165259. The next prime is 21660165277. The reversal of 21660165266 is 66256106612.

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

It can be written as a sum of positive squares in only one way, i.e., 20694261025 + 965904241 = 143855^2 + 31079^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5415041315 + ... + 5415041318.

Almost surely, 2^21660165266 is an apocalyptic number.

21660165266 is a deficient number, since it is larger than the sum of its proper divisors (10830082636).

21660165266 is a wasteful number, since it uses less digits than its factorization.

21660165266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10830082635.

The product of its (nonzero) digits is 155520, while the sum is 41.

The spelling of 21660165266 in words is "twenty-one billion, six hundred sixty million, one hundred sixty-five thousand, two hundred sixty-six".