81129813 has 8 divisors (see below), whose sum is σ = 108216000. Its totient is φ = 54065088.

The previous prime is 81129793. The next prime is 81129823. The reversal of 81129813 is 31892118.

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

It is not a de Polignac number, because 81129813 - 2⁸ = 81129557 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81129823) 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, 8808 + ... + 15486.

It is an arithmetic number, because the mean of its divisors is an integer number (13527000).

Almost surely, 2^81129813 is an apocalyptic number.

It is an amenable number.

81129813 is a deficient number, since it is larger than the sum of its proper divisors (27086187).

81129813 is a wasteful number, since it uses less digits than its factorization.

81129813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10731.

The product of its digits is 3456, while the sum is 33.

The square root of 81129813 is about 9007.2089461719. The cubic root of 81129813 is about 432.9058869147.

The spelling of 81129813 in words is "eighty-one million, one hundred twenty-nine thousand, eight hundred thirteen".