81116640 has 240 divisors, whose sum is σ = 312847920. Its totient is φ = 19630080.

The previous prime is 81116621. The next prime is 81116669. The reversal of 81116640 is 4661118.

81116640 is a `hidden beast` number, since 8 + 1 + 1 + 16 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 142276 + ... + 142844.

It is an arithmetic number, because the mean of its divisors is an integer number (1303533).

Almost surely, 2^81116640 is an apocalyptic number.

81116640 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 81116640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (156423960).

81116640 is an abundant number, since it is smaller than the sum of its proper divisors (231731280).

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

81116640 is a wasteful number, since it uses less digits than its factorization.

81116640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 607 (or 590 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 81116640 is about 9006.4776688781. The cubic root of 81116640 is about 432.8824554217.

Adding to 81116640 its reverse (4661118), we get a palindrome (85777758).

The spelling of 81116640 in words is "eighty-one million, one hundred sixteen thousand, six hundred forty".