161531317 has 2 divisors, whose sum is σ = 161531318. Its totient is φ = 161531316.

The previous prime is 161531303. The next prime is 161531327. The reversal of 161531317 is 713135161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 149964516 + 11566801 = 12246^2 + 3401^2 .

It is an emirp because it is prime and its reverse (713135161) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161531317 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161531327) 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, 80765658 + 80765659.

It is an arithmetic number, because the mean of its divisors is an integer number (80765659).

Almost surely, 2^161531317 is an apocalyptic number.

It is an amenable number.

161531317 is a deficient number, since it is larger than the sum of its proper divisors (1).

161531317 is an equidigital number, since it uses as much as digits as its factorization.

161531317 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1890, while the sum is 28.

The square root of 161531317 is about 12709.4971182970. The cubic root of 161531317 is about 544.6099579971.

Adding to 161531317 its reverse (713135161), we get a palindrome (874666478).

The spelling of 161531317 in words is "one hundred sixty-one million, five hundred thirty-one thousand, three hundred seventeen".