172315981 has 2 divisors, whose sum is σ = 172315982. Its totient is φ = 172315980.

The previous prime is 172315973. The next prime is 172315987. The reversal of 172315981 is 189513271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 168740100 + 3575881 = 12990^2 + 1891^2 .

It is a cyclic number.

It is not a de Polignac number, because 172315981 - 2³ = 172315973 is a prime.

It is a super-2 number, since 2×172315981² = 59385594615984722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 172315981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (172315987) 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, 86157990 + 86157991.

It is an arithmetic number, because the mean of its divisors is an integer number (86157991).

Almost surely, 2^172315981 is an apocalyptic number.

It is an amenable number.

172315981 is a deficient number, since it is larger than the sum of its proper divisors (1).

172315981 is an equidigital number, since it uses as much as digits as its factorization.

172315981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15120, while the sum is 37.

The square root of 172315981 is about 13126.9181836408. The cubic root of 172315981 is about 556.4701234422.

The spelling of 172315981 in words is "one hundred seventy-two million, three hundred fifteen thousand, nine hundred eighty-one".