666157 has 4 divisors (see below), whose sum is σ = 678780. Its totient is φ = 653536.

The previous prime is 666143. The next prime is 666167. The reversal of 666157 is 751666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 751666 = 2 ⋅375833.

It can be written as a sum of positive squares in 2 ways, for example, as 599076 + 67081 = 774^2 + 259^2 .

It is a cyclic number.

It is not a de Polignac number, because 666157 - 2¹¹ = 664109 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666167) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6232 + ... + 6337.

It is an arithmetic number, because the mean of its divisors is an integer number (169695).

2⁶⁶⁶¹⁵⁷ is an apocalyptic number.

It is an amenable number.

666157 is a deficient number, since it is larger than the sum of its proper divisors (12623).

666157 is a wasteful number, since it uses less digits than its factorization.

666157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12622.

The product of its digits is 7560, while the sum is 31.

The square root of 666157 is about 816.1844154356. The cubic root of 666157 is about 87.3357790560.

The spelling of 666157 in words is "six hundred sixty-six thousand, one hundred fifty-seven".