81816784 has 80 divisors (see below), whose sum is σ = 194237568. Its totient is φ = 32587776.

The previous prime is 81816751. The next prime is 81816809. The reversal of 81816784 is 48761818.

It is a super-2 number, since 2×81816784² = 13387972288205312, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81816784.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 184467 + ... + 184909.

Almost surely, 2^81816784 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 81816784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97118784).

81816784 is an abundant number, since it is smaller than the sum of its proper divisors (112420784).

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

81816784 is a wasteful number, since it uses less digits than its factorization.

81816784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 572 (or 566 counting only the distinct ones).

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

The square root of 81816784 is about 9045.2630696957. The cubic root of 81816784 is about 434.1243387857.

The spelling of 81816784 in words is "eighty-one million, eight hundred sixteen thousand, seven hundred eighty-four".