21724264 has 8 divisors (see below), whose sum is σ = 40733010. Its totient is φ = 10862128.

The previous prime is 21724243. The next prime is 21724271. The reversal of 21724264 is 46242712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15760900 + 5963364 = 3970^2 + 2442^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1357759 + ... + 1357774.

Almost surely, 2^21724264 is an apocalyptic number.

It is an amenable number.

21724264 is a deficient number, since it is larger than the sum of its proper divisors (19008746).

21724264 is a wasteful number, since it uses less digits than its factorization.

21724264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2715539 (or 2715535 counting only the distinct ones).

The product of its digits is 5376, while the sum is 28.

The square root of 21724264 is about 4660.9295210290. The cubic root of 21724264 is about 279.0283669123.

Adding to 21724264 its reverse (46242712), we get a palindrome (67966976).

The spelling of 21724264 in words is "twenty-one million, seven hundred twenty-four thousand, two hundred sixty-four".