21645132 has 12 divisors (see below), whose sum is σ = 50505336. Its totient is φ = 7215040.

The previous prime is 21645109. The next prime is 21645133. The reversal of 21645132 is 23154612.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21645133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 901869 + ... + 901892.

It is an arithmetic number, because the mean of its divisors is an integer number (4208778).

Almost surely, 2^21645132 is an apocalyptic number.

It is an amenable number.

21645132 is an abundant number, since it is smaller than the sum of its proper divisors (28860204).

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

21645132 is a wasteful number, since it uses less digits than its factorization.

21645132 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1803768 (or 1803766 counting only the distinct ones).

The product of its digits is 1440, while the sum is 24.

The square root of 21645132 is about 4652.4329119290. The cubic root of 21645132 is about 278.6891619191.

Adding to 21645132 its reverse (23154612), we get a palindrome (44799744).

The spelling of 21645132 in words is "twenty-one million, six hundred forty-five thousand, one hundred thirty-two".