166161275721 has 16 divisors (see below), whose sum is σ = 281331260800. Its totient is φ = 94949300304.

The previous prime is 166161275717. The next prime is 166161275729. The reversal of 166161275721 is 127572161661.

166161275721 is a `hidden beast` number, since 1 + 6 + 6 + 1 + 612 + 7 + 5 + 7 + 21 = 666.

It is not a de Polignac number, because 166161275721 - 2² = 166161275717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166161275729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 439579906 + ... + 439580283.

It is an arithmetic number, because the mean of its divisors is an integer number (17583203800).

Almost surely, 2^166161275721 is an apocalyptic number.

It is an amenable number.

166161275721 is a deficient number, since it is larger than the sum of its proper divisors (115169985079).

166161275721 is an equidigital number, since it uses as much as digits as its factorization.

166161275721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 879160205 (or 879160199 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The spelling of 166161275721 in words is "one hundred sixty-six billion, one hundred sixty-one million, two hundred seventy-five thousand, seven hundred twenty-one".