31521 has 16 divisors (see below), whose sum is σ = 51200. Its totient is φ = 16848.

The previous prime is 31517. The next prime is 31531. The reversal of 31521 is 12513.

31521 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 31521 - 2² = 31517 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a nialpdrome in base 8.

It is a junction number, because it is equal to n+sod(n) for n = 31497 and 31506.

It is not an unprimeable number, because it can be changed into a prime (31511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 360 + ... + 438.

It is an arithmetic number, because the mean of its divisors is an integer number (3200).

2³¹⁵²¹ is an apocalyptic number.

It is an amenable number.

31521 is a deficient number, since it is larger than the sum of its proper divisors (19679).

31521 is a wasteful number, since it uses less digits than its factorization.

31521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108.

The product of its digits is 30, while the sum is 12.

The square root of 31521 is about 177.5415444340. The cubic root of 31521 is about 31.5888146066.

The spelling of 31521 in words is "thirty-one thousand, five hundred twenty-one".