165510991 has 2 divisors, whose sum is σ = 165510992. Its totient is φ = 165510990.

The previous prime is 165510977. The next prime is 165511039. The reversal of 165510991 is 199015561.

It is a weak prime.

It is an emirp because it is prime and its reverse (199015561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 165510991 - 2⁵ = 165510959 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 165510991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165510901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82755495 + 82755496.

It is an arithmetic number, because the mean of its divisors is an integer number (82755496).

Almost surely, 2^165510991 is an apocalyptic number.

165510991 is a deficient number, since it is larger than the sum of its proper divisors (1).

165510991 is an equidigital number, since it uses as much as digits as its factorization.

165510991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12150, while the sum is 37.

The square root of 165510991 is about 12865.1075005225. The cubic root of 165510991 is about 549.0462711069.

The spelling of 165510991 in words is "one hundred sixty-five million, five hundred ten thousand, nine hundred ninety-one".