166177981 has 2 divisors, whose sum is σ = 166177982. Its totient is φ = 166177980.

The previous prime is 166177943. The next prime is 166177987. The reversal of 166177981 is 189771661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 166177881 + 100 = 12891^2 + 10^2 .

It is an emirp because it is prime and its reverse (189771661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 166177981 - 2¹³ = 166169789 is a prime.

It is a super-2 number, since 2×166177981² = 55230242738472722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166177987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83088990 + 83088991.

It is an arithmetic number, because the mean of its divisors is an integer number (83088991).

Almost surely, 2^166177981 is an apocalyptic number.

It is an amenable number.

166177981 is a deficient number, since it is larger than the sum of its proper divisors (1).

166177981 is an equidigital number, since it uses as much as digits as its factorization.

166177981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 127008, while the sum is 46.

The square root of 166177981 is about 12891.0038786745. The cubic root of 166177981 is about 549.7828134212.

The spelling of 166177981 in words is "one hundred sixty-six million, one hundred seventy-seven thousand, nine hundred eighty-one".