81139968 has 360 divisors, whose sum is σ = 304703168. Its totient is φ = 20901888.

The previous prime is 81139957. The next prime is 81139991. The reversal of 81139968 is 86993118.

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

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, 1886955 + ... + 1886997.

Almost surely, 2^81139968 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 81139968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (152351584).

81139968 is an abundant number, since it is smaller than the sum of its proper divisors (223563200).

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

81139968 is a wasteful number, since it uses less digits than its factorization.

81139968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91 (or 68 counting only the distinct ones).

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

The square root of 81139968 is about 9007.7726436672. The cubic root of 81139968 is about 432.9239484045.

It can be divided in two parts, 8113 and 9968, that added together give a palindrome (18081).

The spelling of 81139968 in words is "eighty-one million, one hundred thirty-nine thousand, nine hundred sixty-eight".