161998731 has 32 divisors (see below), whose sum is σ = 253548800. Its totient is φ = 101943360.

The previous prime is 161998717. The next prime is 161998747. The reversal of 161998731 is 137899161.

It is not a de Polignac number, because 161998731 - 2⁵ = 161998699 is a prime.

It is a super-2 number, since 2×161998731² = 52487177691220722, which contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161998531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 234096 + ... + 234786.

It is an arithmetic number, because the mean of its divisors is an integer number (7923400).

Almost surely, 2^161998731 is an apocalyptic number.

161998731 is a deficient number, since it is larger than the sum of its proper divisors (91550069).

161998731 is a wasteful number, since it uses less digits than its factorization.

161998731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1176 (or 1170 counting only the distinct ones).

The product of its digits is 81648, while the sum is 45.

The square root of 161998731 is about 12727.8722102322. The cubic root of 161998731 is about 545.1347544348.

The spelling of 161998731 in words is "one hundred sixty-one million, nine hundred ninety-eight thousand, seven hundred thirty-one".