81865788 has 24 divisors (see below), whose sum is σ = 192713808. Its totient is φ = 27046656.

The previous prime is 81865787. The next prime is 81865789. The reversal of 81865788 is 88756818.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81865787) and next prime (81865789).

It is a self number, because there is not a number n which added to its sum of digits gives 81865788.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81865783) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28831 + ... + 31542.

It is an arithmetic number, because the mean of its divisors is an integer number (8029742).

Almost surely, 2^81865788 is an apocalyptic number.

It is an amenable number.

81865788 is an abundant number, since it is smaller than the sum of its proper divisors (110848020).

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

81865788 is a wasteful number, since it uses less digits than its factorization.

81865788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60493 (or 60491 counting only the distinct ones).

The product of its digits is 860160, while the sum is 51.

The square root of 81865788 is about 9047.9714853662. The cubic root of 81865788 is about 434.2109941237.

The spelling of 81865788 in words is "eighty-one million, eight hundred sixty-five thousand, seven hundred eighty-eight".