166191791 has 4 divisors (see below), whose sum is σ = 166570800. Its totient is φ = 165812784.

The previous prime is 166191787. The next prime is 166191797. The reversal of 166191791 is 197191661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 197191661 = 5563 ⋅35447.

It is a cyclic number.

It is not a de Polignac number, because 166191791 - 2² = 166191787 is a prime.

It is a super-2 number, since 2×166191791² = 55239422791575362, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166191797) 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, 188846 + ... + 189723.

It is an arithmetic number, because the mean of its divisors is an integer number (41642700).

Almost surely, 2^166191791 is an apocalyptic number.

166191791 is a deficient number, since it is larger than the sum of its proper divisors (379009).

166191791 is an equidigital number, since it uses as much as digits as its factorization.

166191791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 379008.

The product of its digits is 20412, while the sum is 41.

The square root of 166191791 is about 12891.5395124089. The cubic root of 166191791 is about 549.7980426557.

The spelling of 166191791 in words is "one hundred sixty-six million, one hundred ninety-one thousand, seven hundred ninety-one".