166128792921 has 81 divisors (see below), whose sum is σ = 302468322429. Its totient is φ = 87569681472.

The previous prime is 166128792919. The next prime is 166128792937. The reversal of 166128792921 is 129297821661.

It is a happy number.

The square root of 166128792921 is 407589.

It is a perfect power (a square), and thus also a powerful number.

166128792921 is a `hidden beast` number, since 16 + 61 + 287 + 9 + 292 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 154032921 + 165974760000 = 12411^2 + 407400^2 .

It is not a de Polignac number, because 166128792921 - 2¹ = 166128792919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (166128792911) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 111271051 + ... + 111272543.

Almost surely, 2^166128792921 is an apocalyptic number.

166128792921 is the 407589-th square number.

166128792921 is the 203795-th centered octagonal number.

It is an amenable number.

166128792921 is a deficient number, since it is larger than the sum of its proper divisors (136339529508).

166128792921 is an equidigital number, since it uses as much as digits as its factorization.

166128792921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3032 (or 1516 counting only the distinct ones).

The product of its digits is 1306368, while the sum is 54.

The spelling of 166128792921 in words is "one hundred sixty-six billion, one hundred twenty-eight million, seven hundred ninety-two thousand, nine hundred twenty-one".