81116881 has 2 divisors, whose sum is σ = 81116882. Its totient is φ = 81116880.

The previous prime is 81116879. The next prime is 81116887. The reversal of 81116881 is 18861118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 62489025 + 18627856 = 7905^2 + 4316^2 .

It is a cyclic number.

It is not a de Polignac number, because 81116881 - 2¹ = 81116879 is a prime.

It is a super-2 number, since 2×81116881² = 13159896766336322, which contains 22 as substring.

Together with 81116879, it forms a pair of twin primes.

It is equal to p_4730938 and since 81116881 and 4730938 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81116887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40558440 + 40558441.

It is an arithmetic number, because the mean of its divisors is an integer number (40558441).

Almost surely, 2^81116881 is an apocalyptic number.

It is an amenable number.

81116881 is a deficient number, since it is larger than the sum of its proper divisors (1).

81116881 is an equidigital number, since it uses as much as digits as its factorization.

81116881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3072, while the sum is 34.

The square root of 81116881 is about 9006.4910481275. The cubic root of 81116881 is about 432.8828841236.

Adding to 81116881 its reverse (18861118), we get a palindrome (99977999).

The spelling of 81116881 in words is "eighty-one million, one hundred sixteen thousand, eight hundred eighty-one".