81968989 has 2 divisors, whose sum is σ = 81968990. Its totient is φ = 81968988.

The previous prime is 81968903. The next prime is 81969007. The reversal of 81968989 is 98986918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53772889 + 28196100 = 7333^2 + 5310^2 .

It is a cyclic number.

It is not a de Polignac number, because 81968989 - 2⁹ = 81968477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81968189) 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, 40984494 + 40984495.

It is an arithmetic number, because the mean of its divisors is an integer number (40984495).

Almost surely, 2^81968989 is an apocalyptic number.

It is an amenable number.

81968989 is a deficient number, since it is larger than the sum of its proper divisors (1).

81968989 is an equidigital number, since it uses as much as digits as its factorization.

81968989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2239488, while the sum is 58.

The square root of 81968989 is about 9053.6726801890. The cubic root of 81968989 is about 434.3933747140.

The spelling of 81968989 in words is "eighty-one million, nine hundred sixty-eight thousand, nine hundred eighty-nine".