21144224 has 12 divisors (see below), whose sum is σ = 41627754. Its totient is φ = 10572096.

The previous prime is 21144223. The next prime is 21144229. The reversal of 21144224 is 42244112.

It can be written as a sum of positive squares in only one way, i.e., 19536400 + 1607824 = 4420^2 + 1268^2 .

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21144196 and 21144205.

It is not an unprimeable number, because it can be changed into a prime (21144223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330347 + ... + 330410.

Almost surely, 2^21144224 is an apocalyptic number.

It is an amenable number.

21144224 is a deficient number, since it is larger than the sum of its proper divisors (20483530).

21144224 is an equidigital number, since it uses as much as digits as its factorization.

21144224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 660767 (or 660759 counting only the distinct ones).

The product of its digits is 512, while the sum is 20.

The square root of 21144224 is about 4598.2848976548. The cubic root of 21144224 is about 276.5225694359.

Adding to 21144224 its reverse (42244112), we get a palindrome (63388336).

The spelling of 21144224 in words is "twenty-one million, one hundred forty-four thousand, two hundred twenty-four".