165661131 has 4 divisors (see below), whose sum is σ = 220881512. Its totient is φ = 110440752.

The previous prime is 165661127. The next prime is 165661147. The reversal of 165661131 is 131166561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 131166561 = 3 ⋅43722187.

It is not a de Polignac number, because 165661131 - 2² = 165661127 is a prime.

It is a super-2 number, since 2×165661131² = 54887220648398322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165661151) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27610186 + ... + 27610191.

It is an arithmetic number, because the mean of its divisors is an integer number (55220378).

Almost surely, 2^165661131 is an apocalyptic number.

165661131 is a deficient number, since it is larger than the sum of its proper divisors (55220381).

165661131 is an equidigital number, since it uses as much as digits as its factorization.

165661131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55220380.

The product of its digits is 3240, while the sum is 30.

The square root of 165661131 is about 12870.9413408655. The cubic root of 165661131 is about 549.2122397295.

The spelling of 165661131 in words is "one hundred sixty-five million, six hundred sixty-one thousand, one hundred thirty-one".