166186991 has 2 divisors, whose sum is σ = 166186992. Its totient is φ = 166186990.

The previous prime is 166186967. The next prime is 166187027. The reversal of 166186991 is 199681661.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 166186991 - 2¹⁰ = 166185967 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166186961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83093495 + 83093496.

It is an arithmetic number, because the mean of its divisors is an integer number (83093496).

Almost surely, 2^166186991 is an apocalyptic number.

166186991 is a deficient number, since it is larger than the sum of its proper divisors (1).

166186991 is an equidigital number, since it uses as much as digits as its factorization.

166186991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 139968, while the sum is 47.

The square root of 166186991 is about 12891.3533424540. The cubic root of 166186991 is about 549.7927494620.

The spelling of 166186991 in words is "one hundred sixty-six million, one hundred eighty-six thousand, nine hundred ninety-one".