81906384 has 40 divisors (see below), whose sum is σ = 241819840. Its totient is φ = 23401728.

The previous prime is 81906373. The next prime is 81906389. The reversal of 81906384 is 48360918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81906389) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121549 + ... + 122220.

It is an arithmetic number, because the mean of its divisors is an integer number (6045496).

Almost surely, 2^81906384 is an apocalyptic number.

81906384 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

81906384 is an abundant number, since it is smaller than the sum of its proper divisors (159913456).

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

81906384 is a wasteful number, since it uses less digits than its factorization.

81906384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243787 (or 243781 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 39.

The square root of 81906384 is about 9050.2145830914. The cubic root of 81906384 is about 434.2827551408.

The spelling of 81906384 in words is "eighty-one million, nine hundred six thousand, three hundred eighty-four".