81787856 has 20 divisors (see below), whose sum is σ = 166804800. Its totient is φ = 38741472.

The previous prime is 81787847. The next prime is 81787877. The reversal of 81787856 is 65878718.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134216 + ... + 134823.

It is an arithmetic number, because the mean of its divisors is an integer number (8340240).

Almost surely, 2^81787856 is an apocalyptic number.

It is an amenable number.

81787856 is an abundant number, since it is smaller than the sum of its proper divisors (85016944).

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

81787856 is a wasteful number, since it uses less digits than its factorization.

81787856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269066 (or 269060 counting only the distinct ones).

The product of its digits is 752640, while the sum is 50.

The square root of 81787856 is about 9043.6638592995. The cubic root of 81787856 is about 434.0731682368.

The spelling of 81787856 in words is "eighty-one million, seven hundred eighty-seven thousand, eight hundred fifty-six".