31221213 has 16 divisors (see below), whose sum is σ = 42951552. Its totient is φ = 20172000.

The previous prime is 31221193. The next prime is 31221227. The reversal of 31221213 is 31212213.

It is not a de Polignac number, because 31221213 - 2⁵ = 31221181 is a prime.

It is a hoax number, since the sum of its digits (15) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 31221192 and 31221201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31221283) 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, 206688 + ... + 206838.

It is an arithmetic number, because the mean of its divisors is an integer number (2684472).

Almost surely, 2^31221213 is an apocalyptic number.

It is an amenable number.

31221213 is a deficient number, since it is larger than the sum of its proper divisors (11730339).

31221213 is an frugal number, since it uses more digits than its factorization.

31221213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277 (or 195 counting only the distinct ones).

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

The square root of 31221213 is about 5587.5945629582. The cubic root of 31221213 is about 314.8835145007.

Adding to 31221213 its reverse (31212213), we get a palindrome (62433426).

The spelling of 31221213 in words is "thirty-one million, two hundred twenty-one thousand, two hundred thirteen".