168172981 has 2 divisors, whose sum is σ = 168172982. Its totient is φ = 168172980.

The previous prime is 168172897. The next prime is 168172999. The reversal of 168172981 is 189271861.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 140778225 + 27394756 = 11865^2 + 5234^2 .

It is a cyclic number.

It is not a de Polignac number, because 168172981 - 2⁷ = 168172853 is a prime.

It is a super-2 number, since 2×168172981² = 56564303076852722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (168172681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 84086490 + 84086491.

It is an arithmetic number, because the mean of its divisors is an integer number (84086491).

Almost surely, 2^168172981 is an apocalyptic number.

It is an amenable number.

168172981 is a deficient number, since it is larger than the sum of its proper divisors (1).

168172981 is an equidigital number, since it uses as much as digits as its factorization.

168172981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 43.

The square root of 168172981 is about 12968.1525669619. The cubic root of 168172981 is about 551.9741518475.

The spelling of 168172981 in words is "one hundred sixty-eight million, one hundred seventy-two thousand, nine hundred eighty-one".