165916521 has 12 divisors (see below), whose sum is σ = 240231940. Its totient is φ = 110345760.

The previous prime is 165916519. The next prime is 165916529. The reversal of 165916521 is 125619561.

165916521 is a `hidden beast` number, since 1 + 6 + 591 + 65 + 2 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 55666521 + 110250000 = 7461^2 + 10500^2 .

It is not a de Polignac number, because 165916521 - 2¹ = 165916519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165916529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18106 + ... + 25683.

Almost surely, 2^165916521 is an apocalyptic number.

It is an amenable number.

165916521 is a deficient number, since it is larger than the sum of its proper divisors (74315419).

165916521 is a wasteful number, since it uses less digits than its factorization.

165916521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44216 (or 44213 counting only the distinct ones).

The product of its digits is 16200, while the sum is 36.

The square root of 165916521 is about 12880.8587058472. The cubic root of 165916521 is about 549.4943241995.

The spelling of 165916521 in words is "one hundred sixty-five million, nine hundred sixteen thousand, five hundred twenty-one".