21644144 has 20 divisors (see below), whose sum is σ = 42014424. Its totient is φ = 10801728.

The previous prime is 21644113. The next prime is 21644153. The reversal of 21644144 is 44144612.

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, 11219 + ... + 13005.

Almost surely, 2^21644144 is an apocalyptic number.

It is an amenable number.

21644144 is a deficient number, since it is larger than the sum of its proper divisors (20370280).

21644144 is a wasteful number, since it uses less digits than its factorization.

21644144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2552 (or 2546 counting only the distinct ones).

The product of its digits is 3072, while the sum is 26.

The square root of 21644144 is about 4652.3267297128. The cubic root of 21644144 is about 278.6849215649.

Adding to 21644144 its reverse (44144612), we get a palindrome (65788756).

The spelling of 21644144 in words is "twenty-one million, six hundred forty-four thousand, one hundred forty-four".