21724307 has 4 divisors (see below), whose sum is σ = 23699256. Its totient is φ = 19749360.

The previous prime is 21724303. The next prime is 21724309. The reversal of 21724307 is 70342712.

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 21724307 - 2² = 21724303 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21724303) 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, 987458 + ... + 987479.

It is an arithmetic number, because the mean of its divisors is an integer number (5924814).

Almost surely, 2^21724307 is an apocalyptic number.

21724307 is a deficient number, since it is larger than the sum of its proper divisors (1974949).

21724307 is a wasteful number, since it uses less digits than its factorization.

21724307 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1974948.

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 21724307 is about 4660.9341338406. The cubic root of 21724307 is about 279.0285510108.

The spelling of 21724307 in words is "twenty-one million, seven hundred twenty-four thousand, three hundred seven".