81331968 has 72 divisors (see below), whose sum is σ = 218323728. Its totient is φ = 26877952.

The previous prime is 81331919. The next prime is 81331973. The reversal of 81331968 is 86913318.

It is a super-2 number, since 2×81331968² = 13229778037506048, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 104830 + ... + 105602.

It is an arithmetic number, because the mean of its divisors is an integer number (3032274).

Almost surely, 2^81331968 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 81331968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109161864).

81331968 is an abundant number, since it is smaller than the sum of its proper divisors (136991760).

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

81331968 is a wasteful number, since it uses less digits than its factorization.

81331968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 929 (or 915 counting only the distinct ones).

The product of its digits is 31104, while the sum is 39.

The square root of 81331968 is about 9018.4238090700. The cubic root of 81331968 is about 433.2651527181.

It can be divided in two parts, 8133 and 1968, that added together give a palindrome (10101).

The spelling of 81331968 in words is "eighty-one million, three hundred thirty-one thousand, nine hundred sixty-eight".