81503729 has 4 divisors (see below), whose sum is σ = 86298084. Its totient is φ = 76709376.

The previous prime is 81503713. The next prime is 81503731. The reversal of 81503729 is 92730518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 92730518 = 2 ⋅46365259.

It can be written as a sum of positive squares in 2 ways, for example, as 44622400 + 36881329 = 6680^2 + 6073^2 .

It is a cyclic number.

It is not a de Polignac number, because 81503729 - 2⁴ = 81503713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81500729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2397152 + ... + 2397185.

It is an arithmetic number, because the mean of its divisors is an integer number (21574521).

Almost surely, 2^81503729 is an apocalyptic number.

It is an amenable number.

81503729 is a deficient number, since it is larger than the sum of its proper divisors (4794355).

81503729 is a wasteful number, since it uses less digits than its factorization.

81503729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4794354.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 81503729 is about 9027.9415704800. The cubic root of 81503729 is about 433.5699354191.

The spelling of 81503729 in words is "eighty-one million, five hundred three thousand, seven hundred twenty-nine".