166557665 has 4 divisors (see below), whose sum is σ = 199869204. Its totient is φ = 133246128.

The previous prime is 166557659. The next prime is 166557673. The reversal of 166557665 is 566755661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 566755661 = 127 ⋅4462643.

It can be written as a sum of positive squares in 2 ways, for example, as 125238481 + 41319184 = 11191^2 + 6428^2 .

It is a cyclic number.

It is not a de Polignac number, because 166557665 - 2¹⁴ = 166541281 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16655762 + ... + 16655771.

It is an arithmetic number, because the mean of its divisors is an integer number (49967301).

Almost surely, 2^166557665 is an apocalyptic number.

It is an amenable number.

166557665 is a deficient number, since it is larger than the sum of its proper divisors (33311539).

166557665 is an equidigital number, since it uses as much as digits as its factorization.

166557665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33311538.

The product of its digits is 1134000, while the sum is 47.

The square root of 166557665 is about 12905.7221804903. The cubic root of 166557665 is about 550.2012101276.

The spelling of 166557665 in words is "one hundred sixty-six million, five hundred fifty-seven thousand, six hundred sixty-five".