81786817 has 24 divisors (see below), whose sum is σ = 98133120. Its totient is φ = 66749760.

The previous prime is 81786799. The next prime is 81786821. The reversal of 81786817 is 71868718.

It is not a de Polignac number, because 81786817 - 2²³ = 73398209 is a prime.

It is a Smith number, since the sum of its digits (46) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81783817) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 918909 + ... + 918997.

It is an arithmetic number, because the mean of its divisors is an integer number (4088880).

Almost surely, 2^81786817 is an apocalyptic number.

It is an amenable number.

81786817 is a deficient number, since it is larger than the sum of its proper divisors (16346303).

81786817 is an equidigital number, since it uses as much as digits as its factorization.

81786817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253 (or 210 counting only the distinct ones).

The product of its digits is 150528, while the sum is 46.

The square root of 81786817 is about 9043.6064155844. The cubic root of 81786817 is about 434.0713301321.

The spelling of 81786817 in words is "eighty-one million, seven hundred eighty-six thousand, eight hundred seventeen".