Subtracting from 13521 its reverse (12531), we obtain a triangular number (990 = T44).
13521 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.
13521 is an esthetic number in base 8, because in such base its adjacent digits differ by 1.
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, and also an emirpimes, since its reverse is a distinct semiprime: 12531 = 3 ⋅4177.
It is a D-number.
It is a Duffinian number.
It is a Curzon number.
213521 is an apocalyptic number.
It is an amenable number.
13521 is an equidigital number, since it uses as much as digits as its factorization.
13521 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 4510.
The square root of 13521 is about 116.2798348812. The cubic root of 13521 is about 23.8233558358.
The spelling of 13521 in words is "thirteen thousand, five hundred twenty-one".