166199881 has 2 divisors, whose sum is σ = 166199882. Its totient is φ = 166199880.

The previous prime is 166199879. The next prime is 166199911. The reversal of 166199881 is 188991661.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 145805625 + 20394256 = 12075^2 + 4516^2 .

It is a cyclic number.

It is not a de Polignac number, because 166199881 - 2¹ = 166199879 is a prime.

It is a super-2 number, since 2×166199881² = 55244800888828322, which contains 22 as substring.

Together with 166199879, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (166199581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83099940 + 83099941.

It is an arithmetic number, because the mean of its divisors is an integer number (83099941).

Almost surely, 2^166199881 is an apocalyptic number.

It is an amenable number.

166199881 is a deficient number, since it is larger than the sum of its proper divisors (1).

166199881 is an equidigital number, since it uses as much as digits as its factorization.

166199881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 186624, while the sum is 49.

The square root of 166199881 is about 12891.8532802697. The cubic root of 166199881 is about 549.8069636619.

The spelling of 166199881 in words is "one hundred sixty-six million, one hundred ninety-nine thousand, eight hundred eighty-one".