166558391 has 2 divisors, whose sum is σ = 166558392. Its totient is φ = 166558390.

The previous prime is 166558331. The next prime is 166558417. The reversal of 166558391 is 193855661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 166558391 - 2²⁶ = 99449527 is a prime.

It is a super-2 number, since 2×166558391² = 55483395225017762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166558321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83279195 + 83279196.

It is an arithmetic number, because the mean of its divisors is an integer number (83279196).

Almost surely, 2^166558391 is an apocalyptic number.

166558391 is a deficient number, since it is larger than the sum of its proper divisors (1).

166558391 is an equidigital number, since it uses as much as digits as its factorization.

166558391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 194400, while the sum is 44.

The square root of 166558391 is about 12905.7503075180. The cubic root of 166558391 is about 550.2020095414.

The spelling of 166558391 in words is "one hundred sixty-six million, five hundred fifty-eight thousand, three hundred ninety-one".