21724619 has 12 divisors (see below), whose sum is σ = 26206704. Its totient is φ = 17638992.

The previous prime is 21724613. The next prime is 21724621. The reversal of 21724619 is 91642712.

It is a happy number.

It is not a de Polignac number, because 21724619 - 2¹⁶ = 21659083 is a prime.

It is a super-3 number, since 3×21724619³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

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 11 ways as a sum of consecutive naturals, for example, 1772 + ... + 6825.

It is an arithmetic number, because the mean of its divisors is an integer number (2183892).

Almost surely, 2^21724619 is an apocalyptic number.

21724619 is a deficient number, since it is larger than the sum of its proper divisors (4482085).

21724619 is an equidigital number, since it uses as much as digits as its factorization.

21724619 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8642 (or 8623 counting only the distinct ones).

The product of its digits is 6048, while the sum is 32.

The square root of 21724619 is about 4660.9676034060. The cubic root of 21724619 is about 279.0298867878.

The spelling of 21724619 in words is "twenty-one million, seven hundred twenty-four thousand, six hundred nineteen".