81507729 has 16 divisors (see below), whose sum is σ = 111310848. Its totient is φ = 53028432.

The previous prime is 81507709. The next prime is 81507731. The reversal of 81507729 is 92770518.

It is not a de Polignac number, because 81507729 - 2²¹ = 79410577 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81507709) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 68074 + ... + 69260.

It is an arithmetic number, because the mean of its divisors is an integer number (6956928).

Almost surely, 2^81507729 is an apocalyptic number.

It is an amenable number.

81507729 is a deficient number, since it is larger than the sum of its proper divisors (29803119).

81507729 is a wasteful number, since it uses less digits than its factorization.

81507729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1724.

The product of its (nonzero) digits is 35280, while the sum is 39.

The square root of 81507729 is about 9028.1631022041. The cubic root of 81507729 is about 433.5770281473.

The spelling of 81507729 in words is "eighty-one million, five hundred seven thousand, seven hundred twenty-nine".