161998531 has 2 divisors, whose sum is σ = 161998532. Its totient is φ = 161998530.

The previous prime is 161998511. The next prime is 161998547. The reversal of 161998531 is 135899161.

It is a strong prime.

It is an emirp because it is prime and its reverse (135899161) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 161998531 - 2⁹ = 161998019 is a prime.

It is a super-2 number, since 2×161998531² = 52487048092315922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (161998511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80999265 + 80999266.

It is an arithmetic number, because the mean of its divisors is an integer number (80999266).

Almost surely, 2^161998531 is an apocalyptic number.

161998531 is a deficient number, since it is larger than the sum of its proper divisors (1).

161998531 is an equidigital number, since it uses as much as digits as its factorization.

161998531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 58320, while the sum is 43.

The square root of 161998531 is about 12727.8643534569. The cubic root of 161998531 is about 545.1345300977.

The spelling of 161998531 in words is "one hundred sixty-one million, nine hundred ninety-eight thousand, five hundred thirty-one".