81330989 has 2 divisors, whose sum is σ = 81330990. Its totient is φ = 81330988.

The previous prime is 81330973. The next prime is 81331027. The reversal of 81330989 is 98903318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72675625 + 8655364 = 8525^2 + 2942^2 .

It is a cyclic number.

It is not a de Polignac number, because 81330989 - 2⁴ = 81330973 is a prime.

It is a super-2 number, since 2×81330989² = 13229459543436242, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81330929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40665494 + 40665495.

It is an arithmetic number, because the mean of its divisors is an integer number (40665495).

Almost surely, 2^81330989 is an apocalyptic number.

It is an amenable number.

81330989 is a deficient number, since it is larger than the sum of its proper divisors (1).

81330989 is an equidigital number, since it uses as much as digits as its factorization.

81330989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 41.

The square root of 81330989 is about 9018.3695311292. The cubic root of 81330989 is about 433.2634142943.

The spelling of 81330989 in words is "eighty-one million, three hundred thirty thousand, nine hundred eighty-nine".