21724210 has 32 divisors (see below), whose sum is σ = 40124160. Its totient is φ = 8466432.

The previous prime is 21724207. The next prime is 21724229. The reversal of 21724210 is 1242712.

It is a happy number.

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 in 15 ways as a sum of consecutive naturals, for example, 84402 + ... + 84658.

It is an arithmetic number, because the mean of its divisors is an integer number (1253880).

Almost surely, 2^21724210 is an apocalyptic number.

21724210 is a deficient number, since it is larger than the sum of its proper divisors (18399950).

21724210 is a wasteful number, since it uses less digits than its factorization.

21724210 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 450.

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 21724210 is about 4660.9237281895. The cubic root of 21724210 is about 279.0281357185.

Adding to 21724210 its reverse (1242712), we get a palindrome (22966922).

The spelling of 21724210 in words is "twenty-one million, seven hundred twenty-four thousand, two hundred ten".