81550729 has 8 divisors (see below), whose sum is σ = 89481672. Its totient is φ = 73856640.

The previous prime is 81550657. The next prime is 81550753. The reversal of 81550729 is 92705518.

It can be written as a sum of positive squares in 4 ways, for example, as 33039504 + 48511225 = 5748^2 + 6965^2 .

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

It is not a de Polignac number, because 81550729 - 2¹¹ = 81548681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81550759) 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, 58492 + ... + 59869.

It is an arithmetic number, because the mean of its divisors is an integer number (11185209).

Almost surely, 2^81550729 is an apocalyptic number.

It is an amenable number.

81550729 is a deficient number, since it is larger than the sum of its proper divisors (7930943).

81550729 is a wasteful number, since it uses less digits than its factorization.

81550729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118427.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 81550729 is about 9030.5442250177. The cubic root of 81550729 is about 433.6532603232.

The spelling of 81550729 in words is "eighty-one million, five hundred fifty thousand, seven hundred twenty-nine".