13621 has 4 divisors (see below), whose sum is σ = 13932. Its totient is φ = 13312.

The previous prime is 13619. The next prime is 13627. The reversal of 13621 is 12631.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12631 = 17 ⋅743.

It can be written as a sum of positive squares in 2 ways, for example, as 12100 + 1521 = 110^2 + 39^2 .

It is a cyclic number.

It is not a de Polignac number, because 13621 - 2¹ = 13619 is a prime.

It is a Duffinian number.

13621 is an undulating number in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13627) 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, 76 + ... + 181.

It is an arithmetic number, because the mean of its divisors is an integer number (3483).

2¹³⁶²¹ is an apocalyptic number.

It is an amenable number.

13621 is a deficient number, since it is larger than the sum of its proper divisors (311).

13621 is an equidigital number, since it uses as much as digits as its factorization.

13621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310.

The product of its digits is 36, while the sum is 13.

The square root of 13621 is about 116.7090399241. The cubic root of 13621 is about 23.8819433768.

Subtracting from 13621 its reverse (12631), we obtain a triangular number (990 = T₄₄).

The spelling of 13621 in words is "thirteen thousand, six hundred twenty-one".