81189729 has 32 divisors (see below), whose sum is σ = 125479040. Its totient is φ = 51834816.

The previous prime is 81189697. The next prime is 81189737. The reversal of 81189729 is 92798118.

It is not a de Polignac number, because 81189729 - 2⁵ = 81189697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81189749) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 66327 + ... + 67539.

It is an arithmetic number, because the mean of its divisors is an integer number (3921220).

Almost surely, 2^81189729 is an apocalyptic number.

It is an amenable number.

81189729 is a deficient number, since it is larger than the sum of its proper divisors (44289311).

81189729 is a wasteful number, since it uses less digits than its factorization.

81189729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1326 (or 1320 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 81189729 is about 9010.5343348771. The cubic root of 81189729 is about 433.0124305946.

It can be divided in two parts, 81189 and 729, that added together give a palindrome (81918).

The spelling of 81189729 in words is "eighty-one million, one hundred eighty-nine thousand, seven hundred twenty-nine".