21724618 has 8 divisors (see below), whose sum is σ = 32607648. Its totient is φ = 10855404.

The previous prime is 21724613. The next prime is 21724621. The reversal of 21724618 is 81642712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21724618.

It is not an unprimeable number, because it can be changed into a prime (21724613) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2605 + ... + 7087.

It is an arithmetic number, because the mean of its divisors is an integer number (4075956).

Almost surely, 2^21724618 is an apocalyptic number.

21724618 is a deficient number, since it is larger than the sum of its proper divisors (10883030).

21724618 is a wasteful number, since it uses less digits than its factorization.

21724618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6908.

The product of its digits is 5376, while the sum is 31.

The square root of 21724618 is about 4660.9674961321. The cubic root of 21724618 is about 279.0298825065.

The spelling of 21724618 in words is "twenty-one million, seven hundred twenty-four thousand, six hundred eighteen".