161191666 has 4 divisors (see below), whose sum is σ = 241787502. Its totient is φ = 80595832.

The previous prime is 161191651. The next prime is 161191673. The reversal of 161191666 is 666191161.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 144504441 + 16687225 = 12021^2 + 4085^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40297915 + ... + 40297918.

Almost surely, 2^161191666 is an apocalyptic number.

161191666 is a deficient number, since it is larger than the sum of its proper divisors (80595836).

161191666 is an equidigital number, since it uses as much as digits as its factorization.

161191666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80595835.

The product of its digits is 11664, while the sum is 37.

The square root of 161191666 is about 12696.1279924235. The cubic root of 161191666 is about 544.2279740322.

The spelling of 161191666 in words is "one hundred sixty-one million, one hundred ninety-one thousand, six hundred sixty-six".