21724099 has 4 divisors (see below), whose sum is σ = 21968280. Its totient is φ = 21479920.

The previous prime is 21724097. The next prime is 21724111. The reversal of 21724099 is 99042712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21724099 - 2¹ = 21724097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21724091) 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, 121957 + ... + 122134.

It is an arithmetic number, because the mean of its divisors is an integer number (5492070).

Almost surely, 2^21724099 is an apocalyptic number.

21724099 is a deficient number, since it is larger than the sum of its proper divisors (244181).

21724099 is an equidigital number, since it uses as much as digits as its factorization.

21724099 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 244180.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 21724099 is about 4660.9118206634. The cubic root of 21724099 is about 279.0276604856.

The spelling of 21724099 in words is "twenty-one million, seven hundred twenty-four thousand, ninety-nine".