21645044 has 12 divisors (see below), whose sum is σ = 37939524. Its totient is φ = 10805184.

The previous prime is 21645023. The next prime is 21645053. The reversal of 21645044 is 44054612.

It can be written as a sum of positive squares in 2 ways, for example, as 13235044 + 8410000 = 3638^2 + 2900^2 .

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, 1289 + ... + 6704.

It is an arithmetic number, because the mean of its divisors is an integer number (3161627).

Almost surely, 2^21645044 is an apocalyptic number.

It is an amenable number.

21645044 is a deficient number, since it is larger than the sum of its proper divisors (16294480).

21645044 is a wasteful number, since it uses less digits than its factorization.

21645044 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8674 (or 8672 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 26.

The square root of 21645044 is about 4652.4234545020. The cubic root of 21645044 is about 278.6887842410.

Adding to 21645044 its reverse (44054612), we get a palindrome (65699656).

The spelling of 21645044 in words is "twenty-one million, six hundred forty-five thousand, forty-four".