165800521 has 4 divisors (see below), whose sum is σ = 165826512. Its totient is φ = 165774532.

The previous prime is 165800513. The next prime is 165800527. The reversal of 165800521 is 125008561.

165800521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 165800521 - 2³ = 165800513 is a prime.

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 165800521.

It is not an unprimeable number, because it can be changed into a prime (165800527) 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, 3870 + ... + 18616.

It is an arithmetic number, because the mean of its divisors is an integer number (41456628).

Almost surely, 2^165800521 is an apocalyptic number.

It is an amenable number.

165800521 is a deficient number, since it is larger than the sum of its proper divisors (25991).

165800521 is a wasteful number, since it uses less digits than its factorization.

165800521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25990.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 165800521 is about 12876.3551131522. The cubic root of 165800521 is about 549.3662352830.

The spelling of 165800521 in words is "one hundred sixty-five million, eight hundred thousand, five hundred twenty-one".