21724456 has 16 divisors (see below), whose sum is σ = 43866900. Its totient is φ = 10026624.

The previous prime is 21724441. The next prime is 21724457. The reversal of 21724456 is 65442712.

It can be written as a sum of positive squares in 2 ways, for example, as 19272100 + 2452356 = 4390^2 + 1566^2 .

It is not an unprimeable number, because it can be changed into a prime (21724457) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 104341 + ... + 104548.

Almost surely, 2^21724456 is an apocalyptic number.

21724456 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21724456 is an abundant number, since it is smaller than the sum of its proper divisors (22142444).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21724456 is a wasteful number, since it uses less digits than its factorization.

21724456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208908 (or 208904 counting only the distinct ones).

The product of its digits is 13440, while the sum is 31.

The square root of 21724456 is about 4660.9501177335. The cubic root of 21724456 is about 279.0291889315.

The spelling of 21724456 in words is "twenty-one million, seven hundred twenty-four thousand, four hundred fifty-six".