165509811 has 20 divisors (see below), whose sum is σ = 249703344. Its totient is φ = 109242000.

The previous prime is 165509801. The next prime is 165509833. The reversal of 165509811 is 118905561.

165509811 is a `hidden beast` number, since 1 + 6 + 550 + 98 + 11 = 666.

It is not a de Polignac number, because 165509811 - 2⁹ = 165509299 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165509801) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1935 + ... + 18296.

Almost surely, 2^165509811 is an apocalyptic number.

165509811 is a deficient number, since it is larger than the sum of its proper divisors (84193533).

165509811 is a wasteful number, since it uses less digits than its factorization.

165509811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20344 (or 20335 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 36.

The square root of 165509811 is about 12865.0616399612. The cubic root of 165509811 is about 549.0449663070.

The spelling of 165509811 in words is "one hundred sixty-five million, five hundred nine thousand, eight hundred eleven".