31521921 has 8 divisors (see below), whose sum is σ = 42056160. Its totient is φ = 21001152.

The previous prime is 31521887. The next prime is 31521953. The reversal of 31521921 is 12912513.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 31521921 - 2⁷ = 31521793 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31521891 and 31521900.

It is not an unprimeable number, because it can be changed into a prime (31521991) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5241 + ... + 9513.

It is an arithmetic number, because the mean of its divisors is an integer number (5257020).

Almost surely, 2^31521921 is an apocalyptic number.

It is an amenable number.

31521921 is a deficient number, since it is larger than the sum of its proper divisors (10534239).

31521921 is a wasteful number, since it uses less digits than its factorization.

31521921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6735.

The product of its digits is 540, while the sum is 24.

The square root of 31521921 is about 5614.4386184195. The cubic root of 31521921 is about 315.8912226408.

The spelling of 31521921 in words is "thirty-one million, five hundred twenty-one thousand, nine hundred twenty-one".