31131221 has 8 divisors (see below), whose sum is σ = 34344000. Its totient is φ = 27982240.

The previous prime is 31131211. The next prime is 31131227. The reversal of 31131221 is 12213113.

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

It is not a de Polignac number, because 31131221 - 2¹⁸ = 30869077 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31131196 and 31131205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31131227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14921 + ... + 16878.

It is an arithmetic number, because the mean of its divisors is an integer number (4293000).

Almost surely, 2^31131221 is an apocalyptic number.

It is an amenable number.

31131221 is a deficient number, since it is larger than the sum of its proper divisors (3212779).

31131221 is a wasteful number, since it uses less digits than its factorization.

31131221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31899.

The product of its digits is 36, while the sum is 14.

The square root of 31131221 is about 5579.5359126006. The cubic root of 31131221 is about 314.5806833551.

Adding to 31131221 its reverse (12213113), we get a palindrome (43344334).

It can be divided in two parts, 3113 and 1221, that added together give a palindrome (4334).

The spelling of 31131221 in words is "thirty-one million, one hundred thirty-one thousand, two hundred twenty-one".