165210991 has 4 divisors (see below), whose sum is σ = 180230184. Its totient is φ = 150191800.

The previous prime is 165210953. The next prime is 165211003. The reversal of 165210991 is 199012561.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 165210991 - 2¹¹ = 165208943 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 (165210091) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7509580 + ... + 7509601.

It is an arithmetic number, because the mean of its divisors is an integer number (45057546).

Almost surely, 2^165210991 is an apocalyptic number.

165210991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

165210991 is a deficient number, since it is larger than the sum of its proper divisors (15019193).

165210991 is a wasteful number, since it uses less digits than its factorization.

165210991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15019192.

The product of its (nonzero) digits is 4860, while the sum is 34.

The square root of 165210991 is about 12853.4427683792. The cubic root of 165210991 is about 548.7143424958.

The spelling of 165210991 in words is "one hundred sixty-five million, two hundred ten thousand, nine hundred ninety-one".