81684780 has 48 divisors (see below), whose sum is σ = 230277600. Its totient is φ = 21634048.

The previous prime is 81684773. The next prime is 81684797. The reversal of 81684780 is 8748618.

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, 4372 + ... + 13508.

It is an arithmetic number, because the mean of its divisors is an integer number (4797450).

Almost surely, 2^81684780 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 81684780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115138800).

81684780 is an abundant number, since it is smaller than the sum of its proper divisors (148592820).

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

81684780 is a wasteful number, since it uses less digits than its factorization.

81684780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9298 (or 9296 counting only the distinct ones).

The product of its (nonzero) digits is 86016, while the sum is 42.

The square root of 81684780 is about 9037.9632661347. The cubic root of 81684780 is about 433.8907396247.

The spelling of 81684780 in words is "eighty-one million, six hundred eighty-four thousand, seven hundred eighty".