161561565 has 48 divisors (see below), whose sum is σ = 309868416. Its totient is φ = 77212800.

The previous prime is 161561549. The next prime is 161561623. The reversal of 161561565 is 565165161.

It is not a de Polignac number, because 161561565 - 2⁴ = 161561549 is a prime.

It is a super-2 number, since 2×161561565² = 52204278570498450, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 32847 + ... + 37443.

It is an arithmetic number, because the mean of its divisors is an integer number (6455592).

Almost surely, 2^161561565 is an apocalyptic number.

161561565 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

161561565 is a deficient number, since it is larger than the sum of its proper divisors (148306851).

161561565 is a wasteful number, since it uses less digits than its factorization.

161561565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4690 (or 4687 counting only the distinct ones).

The product of its digits is 27000, while the sum is 36.

The square root of 161561565 is about 12710.6870388662. The cubic root of 161561565 is about 544.6439500307.

The spelling of 161561565 in words is "one hundred sixty-one million, five hundred sixty-one thousand, five hundred sixty-five".