31123221 has 4 divisors (see below), whose sum is σ = 41497632. Its totient is φ = 20748812.

The previous prime is 31123217. The next prime is 31123229. The reversal of 31123221 is 12232113.

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 a cyclic number.

It is not a de Polignac number, because 31123221 - 2² = 31123217 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31123221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31123229) 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, 5187201 + ... + 5187206.

It is an arithmetic number, because the mean of its divisors is an integer number (10374408).

Almost surely, 2^31123221 is an apocalyptic number.

It is an amenable number.

31123221 is a deficient number, since it is larger than the sum of its proper divisors (10374411).

31123221 is a wasteful number, since it uses less digits than its factorization.

31123221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10374410.

The product of its digits is 72, while the sum is 15.

The square root of 31123221 is about 5578.8189610347. The cubic root of 31123221 is about 314.5537344060.

Adding to 31123221 its reverse (12232113), we get a palindrome (43355334).

It can be divided in two parts, 311 and 23221, that added together give a palindrome (23532).

The spelling of 31123221 in words is "thirty-one million, one hundred twenty-three thousand, two hundred twenty-one".