166666397965971 has 24 divisors (see below), whose sum is σ = 228082330105920. Its totient is φ = 108254220886080.

The previous prime is 166666397965891. The next prime is 166666397965979. The reversal of 166666397965971 is 179569793666661.

It is not a de Polignac number, because 166666397965971 - 2¹⁴ = 166666397949587 is a prime.

It is not an unprimeable number, because it can be changed into a prime (166666397965979) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18633885 + ... + 26087438.

It is an arithmetic number, because the mean of its divisors is an integer number (9503430421080).

Almost surely, 2^{166666397965971} is an apocalyptic number.

166666397965971 is a deficient number, since it is larger than the sum of its proper divisors (61415932139949).

166666397965971 is an equidigital number, since it uses as much as digits as its factorization.

166666397965971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44722147 (or 44722106 counting only the distinct ones).

The product of its digits is 24998984640, while the sum is 87.

The spelling of 166666397965971 in words is "one hundred sixty-six trillion, six hundred sixty-six billion, three hundred ninety-seven million, nine hundred sixty-five thousand, nine hundred seventy-one".