165811997 has 8 divisors (see below), whose sum is σ = 178757880. Its totient is φ = 152893440.

The previous prime is 165811973. The next prime is 165812011. The reversal of 165811997 is 799118561.

165811997 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 13388281 + 152423716 = 3659^2 + 12346^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 165811997 - 2¹⁶ = 165746461 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 (165811907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6797 + ... + 19437.

It is an arithmetic number, because the mean of its divisors is an integer number (22344735).

Almost surely, 2^165811997 is an apocalyptic number.

It is an amenable number.

165811997 is a deficient number, since it is larger than the sum of its proper divisors (12945883).

165811997 is a wasteful number, since it uses less digits than its factorization.

165811997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13663.

The product of its digits is 136080, while the sum is 47.

The square root of 165811997 is about 12876.8007284418. The cubic root of 165811997 is about 549.3789099144.

The spelling of 165811997 in words is "one hundred sixty-five million, eight hundred eleven thousand, nine hundred ninety-seven".