31491921289 has 2 divisors, whose sum is σ = 31491921290. Its totient is φ = 31491921288.

The previous prime is 31491921257. The next prime is 31491921311. The reversal of 31491921289 is 98212919413.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16865437689 + 14626483600 = 129867^2 + 120940^2 .

It is a cyclic number.

It is not a de Polignac number, because 31491921289 - 2⁵ = 31491921257 is a prime.

It is a super-2 number, since 2×31491921289² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (31491921239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15745960644 + 15745960645.

It is an arithmetic number, because the mean of its divisors is an integer number (15745960645).

Almost surely, 2^31491921289 is an apocalyptic number.

It is an amenable number.

31491921289 is a deficient number, since it is larger than the sum of its proper divisors (1).

31491921289 is an equidigital number, since it uses as much as digits as its factorization.

31491921289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 279936, while the sum is 49.

The spelling of 31491921289 in words is "thirty-one billion, four hundred ninety-one million, nine hundred twenty-one thousand, two hundred eighty-nine".