3521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
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: 1253 = 7 ⋅179.
It is a cyclic number.
It is a Curzon number.
It is a plaindrome in base 13.
It is a nialpdrome in base 16.
23521 is an apocalyptic number.
It is an amenable number.
3521 is an equidigital number, since it uses as much as digits as its factorization.
3521 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 510.
The square root of 3521 is about 59.3380147966. The cubic root of 3521 is about 15.2132502190.
Adding to 3521 its reverse (1253), we get a palindrome (4774).
The spelling of 3521 in words is "three thousand, five hundred twenty-one".