31113021221 has 2 divisors, whose sum is σ = 31113021222.
Its totient is φ = 31113021220.
The previous prime is 31113021197. The next prime is 31113021293. The reversal of 31113021221 is 12212031113.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 30385370596 + 727650625 = 174314^2 + 26975^2
It is an emirp because it is prime and its reverse (12212031113) is a distict prime.
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-31113021221 is a prime.
It is a self number, because there is not a number n which added to its sum of digits gives 31113021221.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (31113024221) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15556510610 + 15556510611.
It is an arithmetic number, because the mean of its divisors is an integer number (15556510611).
Almost surely, 231113021221 is an apocalyptic number.
It is an amenable number.
31113021221 is a deficient number, since it is larger than the sum of its proper divisors (1).
31113021221 is an equidigital number, since it uses as much as digits as its factorization.
31113021221 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 72, while the sum is 17.
Adding to 31113021221 its reverse (12212031113), we get a palindrome (43325052334).
The spelling of 31113021221 in words is "thirty-one billion, one hundred thirteen million, twenty-one thousand, two hundred twenty-one".