31212103121581 has 2 divisors, whose sum is σ = 31212103121582. Its totient is φ = 31212103121580.

The previous prime is 31212103121567. The next prime is 31212103121597. The reversal of 31212103121581 is 18512130121213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18846963833481 + 12365139288100 = 4341309^2 + 3516410^2 .

It is a cyclic number.

It is not a de Polignac number, because 31212103121581 - 2¹⁹ = 31212102597293 is a prime.

It is a super-2 number, since 2×31212103121581² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31212103121081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15606051560790 + 15606051560791.

It is an arithmetic number, because the mean of its divisors is an integer number (15606051560791).

Almost surely, 2^{31212103121581} is an apocalyptic number.

It is an amenable number.

31212103121581 is a deficient number, since it is larger than the sum of its proper divisors (1).

31212103121581 is an equidigital number, since it uses as much as digits as its factorization.

31212103121581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 31.

Adding to 31212103121581 its reverse (18512130121213), we get a palindrome (49724233242794).

The spelling of 31212103121581 in words is "thirty-one trillion, two hundred twelve billion, one hundred three million, one hundred twenty-one thousand, five hundred eighty-one".