81551729 has 12 divisors (see below), whose sum is σ = 95742900. Its totient is φ = 69255648.

The previous prime is 81551719. The next prime is 81551753. The reversal of 81551729 is 92715518.

It can be written as a sum of positive squares in 2 ways, for example, as 47059600 + 34492129 = 6860^2 + 5873^2 .

It is not a de Polignac number, because 81551729 - 2¹² = 81547633 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 81551692 and 81551701.

It is not an unprimeable number, because it can be changed into a prime (81551719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2294 + ... + 12975.

It is an arithmetic number, because the mean of its divisors is an integer number (7978575).

Almost surely, 2^81551729 is an apocalyptic number.

It is an amenable number.

81551729 is a deficient number, since it is larger than the sum of its proper divisors (14191171).

81551729 is a wasteful number, since it uses less digits than its factorization.

81551729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15392 (or 15385 counting only the distinct ones).

The product of its digits is 25200, while the sum is 38.

The square root of 81551729 is about 9030.5995924966. The cubic root of 81551729 is about 433.6550328456.

The spelling of 81551729 in words is "eighty-one million, five hundred fifty-one thousand, seven hundred twenty-nine".