23721 has 4 divisors (see below), whose sum is σ = 31632. Its totient is φ = 15812.

The previous prime is 23719. The next prime is 23741. The reversal of 23721 is 12732.

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 23721 - 2¹ = 23719 is a prime.

It is a D-number.

23721 is a lucky number.

It is a plaindrome in base 12.

It is a self number, because there is not a number n which added to its sum of digits gives 23721.

It is not an unprimeable number, because it can be changed into a prime (23741) 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, 3951 + ... + 3956.

It is an arithmetic number, because the mean of its divisors is an integer number (7908).

2²³⁷²¹ is an apocalyptic number.

It is an amenable number.

23721 is a deficient number, since it is larger than the sum of its proper divisors (7911).

23721 is an equidigital number, since it uses as much as digits as its factorization.

23721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7910.

The product of its digits is 84, while the sum is 15.

The square root of 23721 is about 154.0162329107. The cubic root of 23721 is about 28.7327811197.

The spelling of 23721 in words is "twenty-three thousand, seven hundred twenty-one", and thus it is an iban number.