81787806 has 80 divisors (see below), whose sum is σ = 191664000. Its totient is φ = 26045712.

The previous prime is 81787789. The next prime is 81787807. The reversal of 81787806 is 60878718.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81787807) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 410895 + ... + 411093.

It is an arithmetic number, because the mean of its divisors is an integer number (2395800).

Almost surely, 2^81787806 is an apocalyptic number.

81787806 is a gapful number since it is divisible by the number (86) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 81787806, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95832000).

81787806 is an abundant number, since it is smaller than the sum of its proper divisors (109876194).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81787806 is a wasteful number, since it uses less digits than its factorization.

81787806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315 (or 306 counting only the distinct ones).

The product of its (nonzero) digits is 150528, while the sum is 45.

The square root of 81787806 is about 9043.6610949327. The cubic root of 81787806 is about 434.0730797817.

The spelling of 81787806 in words is "eighty-one million, seven hundred eighty-seven thousand, eight hundred six".