23209721 has 4 divisors (see below), whose sum is σ = 23226000. Its totient is φ = 23193444.

The previous prime is 23209717. The next prime is 23209729. The reversal of 23209721 is 12790232.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 23209721 - 2² = 23209717 is a prime.

It is a super-2 number, since 2×23209721² = 1077382297795682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (23209729) 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 3 ways as a sum of consecutive naturals, for example, 5771 + ... + 8928.

It is an arithmetic number, because the mean of its divisors is an integer number (5806500).

Almost surely, 2^23209721 is an apocalyptic number.

It is an amenable number.

23209721 is a deficient number, since it is larger than the sum of its proper divisors (16279).

23209721 is a wasteful number, since it uses less digits than its factorization.

23209721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16278.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 23209721 is about 4817.6468322201. The cubic root of 23209721 is about 285.2484588242.

Adding to 23209721 its reverse (12790232), we get a palindrome (35999953).

The spelling of 23209721 in words is "twenty-three million, two hundred nine thousand, seven hundred twenty-one".