161957861 has 8 divisors (see below), whose sum is σ = 184676184. Its totient is φ = 140705280.

The previous prime is 161957833. The next prime is 161957897. The reversal of 161957861 is 168759161.

It can be written as a sum of positive squares in 4 ways, for example, as 20205025 + 141752836 = 4495^2 + 11906^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 161957861 - 2⁶ = 161957797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161957161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 366200 + ... + 366641.

It is an arithmetic number, because the mean of its divisors is an integer number (23084523).

Almost surely, 2^161957861 is an apocalyptic number.

It is an amenable number.

161957861 is a deficient number, since it is larger than the sum of its proper divisors (22718323).

161957861 is a wasteful number, since it uses less digits than its factorization.

161957861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732871.

The product of its digits is 90720, while the sum is 44.

The square root of 161957861 is about 12726.2665774374. The cubic root of 161957861 is about 545.0889073035.

The spelling of 161957861 in words is "one hundred sixty-one million, nine hundred fifty-seven thousand, eight hundred sixty-one".