21681332 has 12 divisors (see below), whose sum is σ = 38031840. Its totient is φ = 10815096.

The previous prime is 21681311. The next prime is 21681347. The reversal of 21681332 is 23318612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4418 + ... + 7929.

It is an arithmetic number, because the mean of its divisors is an integer number (3169320).

Almost surely, 2^21681332 is an apocalyptic number.

It is an amenable number.

21681332 is a deficient number, since it is larger than the sum of its proper divisors (16350508).

21681332 is a wasteful number, since it uses less digits than its factorization.

21681332 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12790 (or 12788 counting only the distinct ones).

The product of its digits is 1728, while the sum is 26.

The square root of 21681332 is about 4656.3217242798. The cubic root of 21681332 is about 278.8444382301.

Adding to 21681332 its reverse (23318612), we get a palindrome (44999944).

The spelling of 21681332 in words is "twenty-one million, six hundred eighty-one thousand, three hundred thirty-two".