81036840 has 64 divisors (see below), whose sum is σ = 244440000. Its totient is φ = 21491712.

The previous prime is 81036829. The next prime is 81036847. The reversal of 81036840 is 4863018.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81036798 and 81036807.

It is not an unprimeable number, because it can be changed into a prime (81036847) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21411 + ... + 24909.

It is an arithmetic number, because the mean of its divisors is an integer number (3819375).

Almost surely, 2^81036840 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 81036840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122220000).

81036840 is an abundant number, since it is smaller than the sum of its proper divisors (163403160).

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

81036840 is a wasteful number, since it uses less digits than its factorization.

81036840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3706 (or 3702 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 81036840 is about 9002.0464340060. The cubic root of 81036840 is about 432.7404567972.

Adding to 81036840 its reverse (4863018), we get a palindrome (85899858).

The spelling of 81036840 in words is "eighty-one million, thirty-six thousand, eight hundred forty".