81858719 has 2 divisors, whose sum is σ = 81858720. Its totient is φ = 81858718.

The previous prime is 81858691. The next prime is 81858727. The reversal of 81858719 is 91785818.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81858719 - 2⁸ = 81858463 is a prime.

It is a super-2 number, since 2×81858719² = 13401699752641922, which contains 22 as substring.

It is a Sophie Germain 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 (81858419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40929359 + 40929360.

It is an arithmetic number, because the mean of its divisors is an integer number (40929360).

Almost surely, 2^81858719 is an apocalyptic number.

81858719 is a deficient number, since it is larger than the sum of its proper divisors (1).

81858719 is an equidigital number, since it uses as much as digits as its factorization.

81858719 is an evil number, because the sum of its binary digits is even.

The product of its digits is 161280, while the sum is 47.

The square root of 81858719 is about 9047.5808368867. The cubic root of 81858719 is about 434.1984959201.

The spelling of 81858719 in words is "eighty-one million, eight hundred fifty-eight thousand, seven hundred nineteen".