21420244 has 24 divisors (see below), whose sum is σ = 38404520. Its totient is φ = 10450944.

The previous prime is 21420233. The next prime is 21420251. The reversal of 21420244 is 44202412.

It can be written as a sum of positive squares in 4 ways, for example, as 3880900 + 17539344 = 1970^2 + 4188^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31492 + ... + 32164.

Almost surely, 2^21420244 is an apocalyptic number.

It is an amenable number.

21420244 is a deficient number, since it is larger than the sum of its proper divisors (16984276).

21420244 is a wasteful number, since it uses less digits than its factorization.

21420244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 859 (or 857 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 19.

The square root of 21420244 is about 4628.2009463721. The cubic root of 21420244 is about 277.7206275078.

Adding to 21420244 its reverse (44202412), we get a palindrome (65622656).

The spelling of 21420244 in words is "twenty-one million, four hundred twenty thousand, two hundred forty-four".