165251421 has 24 divisors (see below), whose sum is σ = 255533824. Its totient is φ = 106608960.

The previous prime is 165251399. The next prime is 165251447. The reversal of 165251421 is 124152561.

165251421 is a `hidden beast` number, since 1 + 652 + 5 + 1 + 4 + 2 + 1 = 666.

It is not a de Polignac number, because 165251421 - 2⁶ = 165251357 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165251491) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3436 + ... + 18501.

Almost surely, 2^165251421 is an apocalyptic number.

It is an amenable number.

165251421 is a deficient number, since it is larger than the sum of its proper divisors (90282403).

165251421 is an equidigital number, since it uses as much as digits as its factorization.

165251421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21983 (or 21971 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 165251421 is about 12855.0154025579. The cubic root of 165251421 is about 548.7590988230.

The spelling of 165251421 in words is "one hundred sixty-five million, two hundred fifty-one thousand, four hundred twenty-one".