165808961 has 6 divisors (see below), whose sum is σ = 169937586. Its totient is φ = 161684400.

The previous prime is 165808949. The next prime is 165808999. The reversal of 165808961 is 169808561.

It can be written as a sum of positive squares in only one way, i.e., 101103025 + 64705936 = 10055^2 + 8044^2 .

It is not a de Polignac number, because 165808961 - 2⁶ = 165808897 is a prime.

It is a super-2 number, since 2×165808961² = 54985223095799042, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165808561) 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 in 5 ways as a sum of consecutive naturals, for example, 81446 + ... + 83456.

It is an arithmetic number, because the mean of its divisors is an integer number (28322931).

Almost surely, 2^165808961 is an apocalyptic number.

It is an amenable number.

165808961 is a deficient number, since it is larger than the sum of its proper divisors (4128625).

165808961 is an frugal number, since it uses more digits than its factorization.

165808961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4063 (or 2052 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 44.

The square root of 165808961 is about 12876.6828414775. The cubic root of 165808961 is about 549.3755568708.

The spelling of 165808961 in words is "one hundred sixty-five million, eight hundred eight thousand, nine hundred sixty-one".