166571991 has 8 divisors (see below), whose sum is σ = 246773360. Its totient is φ = 111047976.

The previous prime is 166571963. The next prime is 166572013. The reversal of 166571991 is 199175661.

It is not a de Polignac number, because 166571991 - 2⁷ = 166571863 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166571591) 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, 3084640 + ... + 3084693.

It is an arithmetic number, because the mean of its divisors is an integer number (30846670).

Almost surely, 2^166571991 is an apocalyptic number.

166571991 is a deficient number, since it is larger than the sum of its proper divisors (80201369).

166571991 is an equidigital number, since it uses as much as digits as its factorization.

166571991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6169342 (or 6169336 counting only the distinct ones).

The product of its digits is 102060, while the sum is 45.

The square root of 166571991 is about 12906.2771936760. The cubic root of 166571991 is about 550.2169843572.

The spelling of 166571991 in words is "one hundred sixty-six million, five hundred seventy-one thousand, nine hundred ninety-one".