31000331981 has 2 divisors, whose sum is σ = 31000331982. Its totient is φ = 31000331980.

The previous prime is 31000331881. The next prime is 31000332061. The reversal of 31000331981 is 18913300013.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23215093225 + 7785238756 = 152365^2 + 88234^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31000331981 is a prime.

It is a super-2 number, since 2×31000331981² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31000331881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15500165990 + 15500165991.

It is an arithmetic number, because the mean of its divisors is an integer number (15500165991).

Almost surely, 2^31000331981 is an apocalyptic number.

It is an amenable number.

31000331981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31000331981 is an equidigital number, since it uses as much as digits as its factorization.

31000331981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 29.

Adding to 31000331981 its reverse (18913300013), we get a palindrome (49913631994).

The spelling of 31000331981 in words is "thirty-one billion, three hundred thirty-one thousand, nine hundred eighty-one".