81117989 has 2 divisors, whose sum is σ = 81117990. Its totient is φ = 81117988.

The previous prime is 81117977. The next prime is 81118003. The reversal of 81117989 is 98971118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 49589764 + 31528225 = 7042^2 + 5615^2 .

It is a cyclic number.

It is not a de Polignac number, because 81117989 - 2⁸ = 81117733 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81117919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40558994 + 40558995.

It is an arithmetic number, because the mean of its divisors is an integer number (40558995).

Almost surely, 2^81117989 is an apocalyptic number.

It is an amenable number.

81117989 is a deficient number, since it is larger than the sum of its proper divisors (1).

81117989 is an equidigital number, since it uses as much as digits as its factorization.

81117989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 44.

The square root of 81117989 is about 9006.5525591094. The cubic root of 81117989 is about 432.8848550740.

The spelling of 81117989 in words is "eighty-one million, one hundred seventeen thousand, nine hundred eighty-nine".