81994785 has 16 divisors (see below), whose sum is σ = 138096960. Its totient is φ = 41428800.

The previous prime is 81994777. The next prime is 81994789. The reversal of 81994785 is 58749918.

It is not a de Polignac number, because 81994785 - 2³ = 81994777 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81994789) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 143566 + ... + 144135.

It is an arithmetic number, because the mean of its divisors is an integer number (8631060).

Almost surely, 2^81994785 is an apocalyptic number.

It is an amenable number.

81994785 is a deficient number, since it is larger than the sum of its proper divisors (56102175).

81994785 is a wasteful number, since it uses less digits than its factorization.

81994785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287728.

The product of its digits is 725760, while the sum is 51.

The square root of 81994785 is about 9055.0971833548. The cubic root of 81994785 is about 434.4389384341.

The spelling of 81994785 in words is "eighty-one million, nine hundred ninety-four thousand, seven hundred eighty-five".