165421521 has 24 divisors (see below), whose sum is σ = 248408160. Its totient is φ = 110007072.

The previous prime is 165421519. The next prime is 165421547. The reversal of 165421521 is 125124561.

165421521 is a `hidden beast` number, since 1 + 654 + 2 + 1 + 5 + 2 + 1 = 666.

It is not a de Polignac number, because 165421521 - 2¹ = 165421519 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (165421591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 159621 + ... + 160653.

It is an arithmetic number, because the mean of its divisors is an integer number (10350340).

Almost surely, 2^165421521 is an apocalyptic number.

It is an amenable number.

165421521 is a deficient number, since it is larger than the sum of its proper divisors (82986639).

165421521 is an equidigital number, since it uses as much as digits as its factorization.

165421521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1707 (or 1695 counting only the distinct ones).

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

The square root of 165421521 is about 12861.6297956363. The cubic root of 165421521 is about 548.9473209330.

The spelling of 165421521 in words is "one hundred sixty-five million, four hundred twenty-one thousand, five hundred twenty-one".