161911531 has 2 divisors, whose sum is σ = 161911532. Its totient is φ = 161911530.

The previous prime is 161911511. The next prime is 161911537. The reversal of 161911531 is 135119161.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 161911531 - 2⁷ = 161911403 is a prime.

It is a super-2 number, since 2×161911531² = 52430687741527922, 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 161911531.

It is not a weakly prime, because it can be changed into another prime (161911537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80955765 + 80955766.

It is an arithmetic number, because the mean of its divisors is an integer number (80955766).

Almost surely, 2^161911531 is an apocalyptic number.

161911531 is a deficient number, since it is larger than the sum of its proper divisors (1).

161911531 is an equidigital number, since it uses as much as digits as its factorization.

161911531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 810, while the sum is 28.

The square root of 161911531 is about 12724.4461962004. The cubic root of 161911531 is about 545.0369259272.

The spelling of 161911531 in words is "one hundred sixty-one million, nine hundred eleven thousand, five hundred thirty-one".