31231921 has 4 divisors (see below), whose sum is σ = 35693632. Its totient is φ = 26770212.

The previous prime is 31231919. The next prime is 31231933. The reversal of 31231921 is 12913213.

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: 12913213 = 103 ⋅125371.

It is not a de Polignac number, because 31231921 - 2¹ = 31231919 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31231892 and 31231901.

It is not an unprimeable number, because it can be changed into a prime (31231951) 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, 2230845 + ... + 2230858.

It is an arithmetic number, because the mean of its divisors is an integer number (8923408).

Almost surely, 2^31231921 is an apocalyptic number.

It is an amenable number.

31231921 is a deficient number, since it is larger than the sum of its proper divisors (4461711).

31231921 is an equidigital number, since it uses as much as digits as its factorization.

31231921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4461710.

The product of its digits is 324, while the sum is 22.

The square root of 31231921 is about 5588.5526748882. The cubic root of 31231921 is about 314.9195091226.

The spelling of 31231921 in words is "thirty-one million, two hundred thirty-one thousand, nine hundred twenty-one".