23309721 has 8 divisors (see below), whose sum is σ = 34532960. Its totient is φ = 15539796.

The previous prime is 23309711. The next prime is 23309731. The reversal of 23309721 is 12790332.

It is an interprime number because it is at equal distance from previous prime (23309711) and next prime (23309731).

It is not a de Polignac number, because 23309721 - 2¹⁴ = 23293337 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 863323 = 23309721 / (2 + 3 + 3 + 0 + 9 + 7 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (23309701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 431635 + ... + 431688.

It is an arithmetic number, because the mean of its divisors is an integer number (4316620).

Almost surely, 2^23309721 is an apocalyptic number.

It is an amenable number.

23309721 is a deficient number, since it is larger than the sum of its proper divisors (11223239).

23309721 is an equidigital number, since it uses as much as digits as its factorization.

23309721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 863332 (or 863326 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 23309721 is about 4828.0141880487. The cubic root of 23309721 is about 285.6575399567.

The spelling of 23309721 in words is "twenty-three million, three hundred nine thousand, seven hundred twenty-one".