165756921 has 16 divisors (see below), whose sum is σ = 246233088. Its totient is φ = 98320400.

The previous prime is 165756889. The next prime is 165756923. The reversal of 165756921 is 129657561.

It is a cyclic number.

It is not a de Polignac number, because 165756921 - 2⁵ = 165756889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165756923) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51885 + ... + 54986.

It is an arithmetic number, because the mean of its divisors is an integer number (15389568).

Almost surely, 2^165756921 is an apocalyptic number.

165756921 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

165756921 is a deficient number, since it is larger than the sum of its proper divisors (80476167).

165756921 is a wasteful number, since it uses less digits than its factorization.

165756921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106932.

The product of its digits is 113400, while the sum is 42.

The square root of 165756921 is about 12874.6619761452. The cubic root of 165756921 is about 549.3180760702.

The spelling of 165756921 in words is "one hundred sixty-five million, seven hundred fifty-six thousand, nine hundred twenty-one".