81128981 has 8 divisors (see below), whose sum is σ = 89636544. Its totient is φ = 73036480.

The previous prime is 81128951. The next prime is 81128987. The reversal of 81128981 is 18982118.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81128981 - 2¹⁰ = 81127957 is a prime.

It is a super-3 number, since 3×81128981³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81128987) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 103355 + ... + 104136.

It is an arithmetic number, because the mean of its divisors is an integer number (11204568).

Almost surely, 2^81128981 is an apocalyptic number.

It is an amenable number.

81128981 is a deficient number, since it is larger than the sum of its proper divisors (8507563).

81128981 is a wasteful number, since it uses less digits than its factorization.

81128981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207531.

The product of its digits is 9216, while the sum is 38.

The square root of 81128981 is about 9007.1627608254. The cubic root of 81128981 is about 432.9044070685.

It can be divided in two parts, 811 and 28981, that added together give a palindrome (29792).

The spelling of 81128981 in words is "eighty-one million, one hundred twenty-eight thousand, nine hundred eighty-one".