81087817 has 2 divisors, whose sum is σ = 81087818. Its totient is φ = 81087816.

The previous prime is 81087779. The next prime is 81087859. The reversal of 81087817 is 71878018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 59660176 + 21427641 = 7724^2 + 4629^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81087817 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81087817.

It is not a weakly prime, because it can be changed into another prime (81087887) 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, 40543908 + 40543909.

It is an arithmetic number, because the mean of its divisors is an integer number (40543909).

Almost surely, 2^81087817 is an apocalyptic number.

It is an amenable number.

81087817 is a deficient number, since it is larger than the sum of its proper divisors (1).

81087817 is an equidigital number, since it uses as much as digits as its factorization.

81087817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25088, while the sum is 40.

The square root of 81087817 is about 9004.8774006091. The cubic root of 81087817 is about 432.8311776193.

The spelling of 81087817 in words is "eighty-one million, eighty-seven thousand, eight hundred seventeen".