81986784 has 96 divisors (see below), whose sum is σ = 248645376. Its totient is φ = 23377920.

The previous prime is 81986771. The next prime is 81986791. The reversal of 81986784 is 48768918.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (51).

Its product of digits (774144) is a multiple of the sum of its prime factors (4608).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15669 + ... + 20235.

It is an arithmetic number, because the mean of its divisors is an integer number (2590056).

Almost surely, 2^81986784 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 81986784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124322688).

81986784 is an abundant number, since it is smaller than the sum of its proper divisors (166658592).

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

81986784 is a wasteful number, since it uses less digits than its factorization.

81986784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4608 (or 4600 counting only the distinct ones).

The product of its digits is 774144, while the sum is 51.

The square root of 81986784 is about 9054.6553772079. The cubic root of 81986784 is about 434.4248072142.

The spelling of 81986784 in words is "eighty-one million, nine hundred eighty-six thousand, seven hundred eighty-four".