21732165 has 128 divisors (see below), whose sum is σ = 49996800. Its totient is φ = 8709120.

The previous prime is 21732131. The next prime is 21732169. The reversal of 21732165 is 56123712.

It is a happy number.

It is not a de Polignac number, because 21732165 - 2⁶ = 21732101 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21732169) 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 127 ways as a sum of consecutive naturals, for example, 356235 + ... + 356295.

It is an arithmetic number, because the mean of its divisors is an integer number (390600).

Almost surely, 2^21732165 is an apocalyptic number.

It is an amenable number.

21732165 is an abundant number, since it is smaller than the sum of its proper divisors (28264635).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21732165 is a wasteful number, since it uses less digits than its factorization.

21732165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124 (or 118 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21732165 is about 4661.7770216946. Note that the first 3 decimals coincide. The cubic root of 21732165 is about 279.0621898597.

Adding to 21732165 its reverse (56123712), we get a palindrome (77855877).

The spelling of 21732165 in words is "twenty-one million, seven hundred thirty-two thousand, one hundred sixty-five".