81261589 has 2 divisors, whose sum is σ = 81261590. Its totient is φ = 81261588.

The previous prime is 81261569. The next prime is 81261617. The reversal of 81261589 is 98516218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43007364 + 38254225 = 6558^2 + 6185^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81261589 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 (81261569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40630794 + 40630795.

It is an arithmetic number, because the mean of its divisors is an integer number (40630795).

Almost surely, 2^81261589 is an apocalyptic number.

It is an amenable number.

81261589 is a deficient number, since it is larger than the sum of its proper divisors (1).

81261589 is an equidigital number, since it uses as much as digits as its factorization.

81261589 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34560, while the sum is 40.

The square root of 81261589 is about 9014.5210077963. The cubic root of 81261589 is about 433.1401441940.

The spelling of 81261589 in words is "eighty-one million, two hundred sixty-one thousand, five hundred eighty-nine".