81618784 has 48 divisors (see below), whose sum is σ = 178657920. Its totient is φ = 36449280.

The previous prime is 81618769. The next prime is 81618791. The reversal of 81618784 is 48781618.

It is a self number, because there is not a number n which added to its sum of digits gives 81618784.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9732 + ... + 16060.

It is an arithmetic number, because the mean of its divisors is an integer number (3722040).

Almost surely, 2^81618784 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81618784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89328960).

81618784 is an abundant number, since it is smaller than the sum of its proper divisors (97039136).

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

81618784 is a wasteful number, since it uses less digits than its factorization.

81618784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6383 (or 6375 counting only the distinct ones).

The product of its digits is 86016, while the sum is 43.

The square root of 81618784 is about 9034.3114845571. The cubic root of 81618784 is about 433.7738562899.

It can be divided in two parts, 816 and 18784, that added together give a square (19600 = 140²).

The spelling of 81618784 in words is "eighty-one million, six hundred eighteen thousand, seven hundred eighty-four".