31221212261 has 2 divisors, whose sum is σ = 31221212262. Its totient is φ = 31221212260.

The previous prime is 31221212203. The next prime is 31221212263. The reversal of 31221212261 is 16221212213.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25120665025 + 6100547236 = 158495^2 + 78106^2 .

It is a cyclic number.

It is not a de Polignac number, because 31221212261 - 2²⁶ = 31154103397 is a prime.

Together with 31221212263, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31221212263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15610606130 + 15610606131.

It is an arithmetic number, because the mean of its divisors is an integer number (15610606131).

Almost surely, 2^31221212261 is an apocalyptic number.

It is an amenable number.

31221212261 is a deficient number, since it is larger than the sum of its proper divisors (1).

31221212261 is an equidigital number, since it uses as much as digits as its factorization.

31221212261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 23.

Adding to 31221212261 its reverse (16221212213), we get a palindrome (47442424474).

The spelling of 31221212261 in words is "thirty-one billion, two hundred twenty-one million, two hundred twelve thousand, two hundred sixty-one".