81891936 has 144 divisors (see below), whose sum is σ = 271908000. Its totient is φ = 23369472.

The previous prime is 81891893. The next prime is 81891949. The reversal of 81891936 is 63919818.

It is a tau number, because it is divible by the number of its divisors (144).

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 81891891 and 81891900.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 98370 + ... + 99198.

It is an arithmetic number, because the mean of its divisors is an integer number (1888250).

Almost surely, 2^81891936 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 81891936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (135954000).

81891936 is an abundant number, since it is smaller than the sum of its proper divisors (190016064).

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

81891936 is a wasteful number, since it uses less digits than its factorization.

81891936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 866 (or 841 counting only the distinct ones).

The product of its digits is 93312, while the sum is 45.

The square root of 81891936 is about 9049.4163347699. The cubic root of 81891936 is about 434.2572183189.

The spelling of 81891936 in words is "eighty-one million, eight hundred ninety-one thousand, nine hundred thirty-six".