161231531 has 2 divisors, whose sum is σ = 161231532. Its totient is φ = 161231530.

The previous prime is 161231509. The next prime is 161231569. The reversal of 161231531 is 135132161.

161231531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161231531 - 2¹⁰ = 161230507 is a prime.

It is a super-2 number, since 2×161231531² = 51991213177207922, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 161231497 and 161231506.

It is not a weakly prime, because it can be changed into another prime (161231431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80615765 + 80615766.

It is an arithmetic number, because the mean of its divisors is an integer number (80615766).

Almost surely, 2^161231531 is an apocalyptic number.

161231531 is a deficient number, since it is larger than the sum of its proper divisors (1).

161231531 is an equidigital number, since it uses as much as digits as its factorization.

161231531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 540, while the sum is 23.

The square root of 161231531 is about 12697.6978622111. The cubic root of 161231531 is about 544.2728354497.

Adding to 161231531 its reverse (135132161), we get a palindrome (296363692).

The spelling of 161231531 in words is "one hundred sixty-one million, two hundred thirty-one thousand, five hundred thirty-one".