21724199 has 12 divisors (see below), whose sum is σ = 25811424. Its totient is φ = 18222624.

The previous prime is 21724193. The next prime is 21724207. The reversal of 21724199 is 99142712.

It is a de Polignac number, because none of the positive numbers 2^k-21724199 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21724193) 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, 2414 + ... + 7019.

It is an arithmetic number, because the mean of its divisors is an integer number (2150952).

Almost surely, 2^21724199 is an apocalyptic number.

21724199 is a deficient number, since it is larger than the sum of its proper divisors (4087225).

21724199 is an equidigital number, since it uses as much as digits as its factorization.

21724199 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9494 (or 9487 counting only the distinct ones).

The product of its digits is 9072, while the sum is 35.

The square root of 21724199 is about 4660.9225481658. The cubic root of 21724199 is about 279.0280886234.

The spelling of 21724199 in words is "twenty-one million, seven hundred twenty-four thousand, one hundred ninety-nine".