31239921 has 4 divisors (see below), whose sum is σ = 41653232. Its totient is φ = 20826612.

The previous prime is 31239919. The next prime is 31239947. The reversal of 31239921 is 12993213.

It is a happy number.

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.

It is not a de Polignac number, because 31239921 - 2¹ = 31239919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31239961) 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, 5206651 + ... + 5206656.

It is an arithmetic number, because the mean of its divisors is an integer number (10413308).

Almost surely, 2^31239921 is an apocalyptic number.

It is an amenable number.

31239921 is a deficient number, since it is larger than the sum of its proper divisors (10413311).

31239921 is a wasteful number, since it uses less digits than its factorization.

31239921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10413310.

The product of its digits is 2916, while the sum is 30.

The square root of 31239921 is about 5589.2683778827. The cubic root of 31239921 is about 314.9463955144.

The spelling of 31239921 in words is "thirty-one million, two hundred thirty-nine thousand, nine hundred twenty-one".