81905100 has 72 divisors (see below), whose sum is σ = 244651008. Its totient is φ = 21134400.

The previous prime is 81905071. The next prime is 81905119. The reversal of 81905100 is 150918.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4897 + ... + 13703.

Almost surely, 2^81905100 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 81905100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122325504).

81905100 is an abundant number, since it is smaller than the sum of its proper divisors (162745908).

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

81905100 is a wasteful number, since it uses less digits than its factorization.

81905100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8855 (or 8848 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 24.

The square root of 81905100 is about 9050.1436452688. The cubic root of 81905100 is about 434.2804857940.

The spelling of 81905100 in words is "eighty-one million, nine hundred five thousand, one hundred".