81107840 has 128 divisors (see below), whose sum is σ = 217455840. Its totient is φ = 28672000.

The previous prime is 81107837. The next prime is 81107843. The reversal of 81107840 is 4870118.

It is an interprime number because it is at equal distance from previous prime (81107837) and next prime (81107843).

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81107843) 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, 288500 + ... + 288780.

Almost surely, 2^81107840 is an apocalyptic number.

81107840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81107840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (108727920).

81107840 is an abundant number, since it is smaller than the sum of its proper divisors (136348000).

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

81107840 is a wasteful number, since it uses less digits than its factorization.

81107840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352 (or 340 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 81107840 is about 9005.9891183590. The cubic root of 81107840 is about 432.8668009955.

Adding to 81107840 its reverse (4870118), we get a palindrome (85977958).

It can be divided in two parts, 811078 and 40, that added together give a palindrome (811118).

The spelling of 81107840 in words is "eighty-one million, one hundred seven thousand, eight hundred forty".