165985861 has 2 divisors, whose sum is σ = 165985862. Its totient is φ = 165985860.

The previous prime is 165985849. The next prime is 165985889. The reversal of 165985861 is 168589561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 114361636 + 51624225 = 10694^2 + 7185^2 .

It is a cyclic number.

It is not a de Polignac number, because 165985861 - 2⁵ = 165985829 is a prime.

It is a super-2 number, since 2×165985861² = 55102612103822642, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165985661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82992930 + 82992931.

It is an arithmetic number, because the mean of its divisors is an integer number (82992931).

Almost surely, 2^165985861 is an apocalyptic number.

It is an amenable number.

165985861 is a deficient number, since it is larger than the sum of its proper divisors (1).

165985861 is an equidigital number, since it uses as much as digits as its factorization.

165985861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 518400, while the sum is 49.

The square root of 165985861 is about 12883.5500154266. The cubic root of 165985861 is about 549.5708619459.

The spelling of 165985861 in words is "one hundred sixty-five million, nine hundred eighty-five thousand, eight hundred sixty-one".