81641936 has 40 divisors (see below), whose sum is σ = 168218400. Its totient is φ = 38275200.

The previous prime is 81641933. The next prime is 81641953. The reversal of 81641936 is 63914618.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a self number, because there is not a number n which added to its sum of digits gives 81641936.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81641933) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 29375 + ... + 32033.

It is an arithmetic number, because the mean of its divisors is an integer number (4205460).

Almost surely, 2^81641936 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 81641936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (84109200).

81641936 is an abundant number, since it is smaller than the sum of its proper divisors (86576464).

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

81641936 is a wasteful number, since it uses less digits than its factorization.

81641936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2787 (or 2781 counting only the distinct ones).

The product of its digits is 31104, while the sum is 38.

The square root of 81641936 is about 9035.5927309723. The cubic root of 81641936 is about 433.8148672043.

The spelling of 81641936 in words is "eighty-one million, six hundred forty-one thousand, nine hundred thirty-six".