31116781 has 2 divisors, whose sum is σ = 31116782. Its totient is φ = 31116780.

The previous prime is 31116731. The next prime is 31116793. The reversal of 31116781 is 18761113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28196100 + 2920681 = 5310^2 + 1709^2 .

It is a cyclic number.

It is not a de Polignac number, because 31116781 - 2¹⁹ = 30592493 is a prime.

It is a super-2 number, since 2×31116781² = 1936508119603922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31116731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15558390 + 15558391.

It is an arithmetic number, because the mean of its divisors is an integer number (15558391).

Almost surely, 2^31116781 is an apocalyptic number.

It is an amenable number.

31116781 is a deficient number, since it is larger than the sum of its proper divisors (1).

31116781 is an equidigital number, since it uses as much as digits as its factorization.

31116781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 28.

The square root of 31116781 is about 5578.2417480780. The cubic root of 31116781 is about 314.5320371467.

Adding to 31116781 its reverse (18761113), we get a palindrome (49877894).

The spelling of 31116781 in words is "thirty-one million, one hundred sixteen thousand, seven hundred eighty-one".