161531 has 2 divisors, whose sum is σ = 161532. Its totient is φ = 161530.

The previous prime is 161527. The next prime is 161543. The reversal of 161531 is 135161.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161531 - 2² = 161527 is a prime.

It is a super-2 number, since 2×161531² = 52184527922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (161521) 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, 80765 + 80766.

It is an arithmetic number, because the mean of its divisors is an integer number (80766).

2¹⁶¹⁵³¹ is an apocalyptic number.

161531 is a deficient number, since it is larger than the sum of its proper divisors (1).

161531 is an equidigital number, since it uses as much as digits as its factorization.

161531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90, while the sum is 17.

The square root of 161531 is about 401.9091937242. The cubic root of 161531 is about 54.4609601737.

Adding to 161531 its reverse (135161), we get a palindrome (296692).

It can be divided in two parts, 161 and 531, that multiplied together give a triangular number (85491 = T₄₁₃).

The spelling of 161531 in words is "one hundred sixty-one thousand, five hundred thirty-one".