21648644 has 12 divisors (see below), whose sum is σ = 37928268. Its totient is φ = 10812000.

The previous prime is 21648631. The next prime is 21648647. The reversal of 21648644 is 44684612.

It can be written as a sum of positive squares in 2 ways, for example, as 4674244 + 16974400 = 2162^2 + 4120^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21648647) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1694 + ... + 6794.

It is an arithmetic number, because the mean of its divisors is an integer number (3160689).

Almost surely, 2^21648644 is an apocalyptic number.

It is an amenable number.

21648644 is a deficient number, since it is larger than the sum of its proper divisors (16279624).

21648644 is a wasteful number, since it uses less digits than its factorization.

21648644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6166 (or 6164 counting only the distinct ones).

The product of its digits is 36864, while the sum is 35.

The square root of 21648644 is about 4652.8103335511. The cubic root of 21648644 is about 278.7042338747.

The spelling of 21648644 in words is "twenty-one million, six hundred forty-eight thousand, six hundred forty-four".