165991297 has 4 divisors (see below), whose sum is σ = 166703940. Its totient is φ = 165278656.

The previous prime is 165991291. The next prime is 165991303. The reversal of 165991297 is 792199561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 792199561 = 4373 ⋅181157.

It is an interprime number because it is at equal distance from previous prime (165991291) and next prime (165991303).

It can be written as a sum of positive squares in 2 ways, for example, as 69872881 + 96118416 = 8359^2 + 9804^2 .

It is a cyclic number.

It is not a de Polignac number, because 165991297 - 2³ = 165991289 is a prime.

It is a super-2 number, since 2×165991297² = 55106221359484418, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 165991297.

It is not an unprimeable number, because it can be changed into a prime (165991291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 355972 + ... + 356437.

It is an arithmetic number, because the mean of its divisors is an integer number (41675985).

Almost surely, 2^165991297 is an apocalyptic number.

It is an amenable number.

165991297 is a deficient number, since it is larger than the sum of its proper divisors (712643).

165991297 is an equidigital number, since it uses as much as digits as its factorization.

165991297 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 712642.

The product of its digits is 306180, while the sum is 49.

The square root of 165991297 is about 12883.7609803970. The cubic root of 165991297 is about 549.5768613215.

The spelling of 165991297 in words is "one hundred sixty-five million, nine hundred ninety-one thousand, two hundred ninety-seven".