21744809 has 8 divisors (see below), whose sum is σ = 22576320. Its totient is φ = 20918800.

The previous prime is 21744803. The next prime is 21744817. The reversal of 21744809 is 90844712.

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

It is a cyclic number.

It is not a de Polignac number, because 21744809 - 2⁸ = 21744553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21744803) 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 7 ways as a sum of consecutive naturals, for example, 7814 + ... + 10224.

It is an arithmetic number, because the mean of its divisors is an integer number (2822040).

Almost surely, 2^21744809 is an apocalyptic number.

21744809 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21744809 is a deficient number, since it is larger than the sum of its proper divisors (831511).

21744809 is a wasteful number, since it uses less digits than its factorization.

21744809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2751.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21744809 is about 4663.1329597171. The cubic root of 21744809 is about 279.1162997969.

The spelling of 21744809 in words is "twenty-one million, seven hundred forty-four thousand, eight hundred nine".