31213321 has 2 divisors, whose sum is σ = 31213322. Its totient is φ = 31213320.

The previous prime is 31213289. The next prime is 31213363. The reversal of 31213321 is 12331213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15721225 + 15492096 = 3965^2 + 3936^2 .

It is an emirp because it is prime and its reverse (12331213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31213321 - 2⁵ = 31213289 is a prime.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 31213295 and 31213304.

It is not a weakly prime, because it can be changed into another prime (31243321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15606660 + 15606661.

It is an arithmetic number, because the mean of its divisors is an integer number (15606661).

Almost surely, 2^31213321 is an apocalyptic number.

It is an amenable number.

31213321 is a deficient number, since it is larger than the sum of its proper divisors (1).

31213321 is an equidigital number, since it uses as much as digits as its factorization.

31213321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108, while the sum is 16.

The square root of 31213321 is about 5586.8883110368. Note that the first 3 decimals coincide. The cubic root of 31213321 is about 314.8569805101.

Adding to 31213321 its reverse (12331213), we get a palindrome (43544534).

The spelling of 31213321 in words is "thirty-one million, two hundred thirteen thousand, three hundred twenty-one".