31123681 has 2 divisors, whose sum is σ = 31123682. Its totient is φ = 31123680.

The previous prime is 31123679. The next prime is 31123723. The reversal of 31123681 is 18632113.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26780625 + 4343056 = 5175^2 + 2084^2 .

It is an emirp because it is prime and its reverse (18632113) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31123681 - 2¹ = 31123679 is a prime.

It is a super-2 number, since 2×31123681² = 1937367037979522, which contains 22 as substring.

Together with 31123679, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (31123601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15561840 + 15561841.

It is an arithmetic number, because the mean of its divisors is an integer number (15561841).

Almost surely, 2^31123681 is an apocalyptic number.

It is an amenable number.

31123681 is a deficient number, since it is larger than the sum of its proper divisors (1).

31123681 is an equidigital number, since it uses as much as digits as its factorization.

31123681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 25.

The square root of 31123681 is about 5578.8601882463. The cubic root of 31123681 is about 314.5552840957. Note that the first 3 decimals are identical.

Adding to 31123681 its reverse (18632113), we get a palindrome (49755794).

The spelling of 31123681 in words is "thirty-one million, one hundred twenty-three thousand, six hundred eighty-one".