161731 has 2 divisors, whose sum is σ = 161732. Its totient is φ = 161730.

The previous prime is 161729. The next prime is 161741. The reversal of 161731 is 137161.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161731 - 2¹ = 161729 is a prime.

It is a super-2 number, since 2×161731² = 52313832722, which contains 22 as substring.

Together with 161729, it forms a pair of twin primes.

161731 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 161699 and 161708.

It is not a weakly prime, because it can be changed into another prime (161741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80865 + 80866.

It is an arithmetic number, because the mean of its divisors is an integer number (80866).

2¹⁶¹⁷³¹ is an apocalyptic number.

161731 is a deficient number, since it is larger than the sum of its proper divisors (1).

161731 is an equidigital number, since it uses as much as digits as its factorization.

161731 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 126, while the sum is 19.

The square root of 161731 is about 402.1579291771. The cubic root of 161731 is about 54.4834278935.

Adding to 161731 its reverse (137161), we get a palindrome (298892).

The spelling of 161731 in words is "one hundred sixty-one thousand, seven hundred thirty-one".