166257721 has 8 divisors (see below), whose sum is σ = 190805760. Its totient is φ = 141908928.

The previous prime is 166257703. The next prime is 166257779. The reversal of 166257721 is 127752661.

166257721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 166257721 - 2¹³ = 166249529 is a prime.

It is a super-2 number, since 2×166257721² = 55283259584227682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166257701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48016 + ... + 51361.

It is an arithmetic number, because the mean of its divisors is an integer number (23850720).

Almost surely, 2^166257721 is an apocalyptic number.

It is an amenable number.

166257721 is a deficient number, since it is larger than the sum of its proper divisors (24548039).

166257721 is an equidigital number, since it uses as much as digits as its factorization.

166257721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99623.

The product of its digits is 35280, while the sum is 37.

The square root of 166257721 is about 12894.0963622892. The cubic root of 166257721 is about 549.8707365645.

The spelling of 166257721 in words is "one hundred sixty-six million, two hundred fifty-seven thousand, seven hundred twenty-one".