13721 has 2 divisors, whose sum is σ = 13722. Its totient is φ = 13720.

The previous prime is 13711. The next prime is 13723. The reversal of 13721 is 12731.

13721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10000 + 3721 = 100^2 + 61^2 .

It is a cyclic number.

It is not a de Polignac number, because 13721 - 2¹⁰ = 12697 is a prime.

Together with 13723, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 13696 and 13705.

It is not a weakly prime, because it can be changed into another prime (13723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6860 + 6861.

It is an arithmetic number, because the mean of its divisors is an integer number (6861).

2¹³⁷²¹ is an apocalyptic number.

It is an amenable number.

13721 is a deficient number, since it is larger than the sum of its proper divisors (1).

13721 is an equidigital number, since it uses as much as digits as its factorization.

13721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 42, while the sum is 14.

The square root of 13721 is about 117.1366723106. The cubic root of 13721 is about 23.9402448638.

Subtracting from 13721 its reverse (12731), we obtain a triangular number (990 = T₄₄).

The spelling of 13721 in words is "thirteen thousand, seven hundred twenty-one".