165285991 has 4 divisors (see below), whose sum is σ = 178000312. Its totient is φ = 152571672.

The previous prime is 165285983. The next prime is 165286007. The reversal of 165285991 is 199582561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199582561 = 131 ⋅1523531.

It is a cyclic number.

It is not a de Polignac number, because 165285991 - 2³ = 165285983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165285931) 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, 6357141 + ... + 6357166.

It is an arithmetic number, because the mean of its divisors is an integer number (44500078).

Almost surely, 2^165285991 is an apocalyptic number.

165285991 is a deficient number, since it is larger than the sum of its proper divisors (12714321).

165285991 is a wasteful number, since it uses less digits than its factorization.

165285991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12714320.

The product of its digits is 194400, while the sum is 46.

The square root of 165285991 is about 12856.3599436232. The cubic root of 165285991 is about 548.7973622949.

The spelling of 165285991 in words is "one hundred sixty-five million, two hundred eighty-five thousand, nine hundred ninety-one".