81803509 has 4 divisors (see below), whose sum is σ = 81823500. Its totient is φ = 81783520.

The previous prime is 81803497. The next prime is 81803521. The reversal of 81803509 is 90530818.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (81803497) and next prime (81803521).

It can be written as a sum of positive squares in 2 ways, for example, as 50722884 + 31080625 = 7122^2 + 5575^2 .

It is a cyclic number.

It is not a de Polignac number, because 81803509 - 2¹³ = 81795317 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81804509) 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 3 ways as a sum of consecutive naturals, for example, 1384 + ... + 12865.

It is an arithmetic number, because the mean of its divisors is an integer number (20455875).

Almost surely, 2^81803509 is an apocalyptic number.

It is an amenable number.

81803509 is a deficient number, since it is larger than the sum of its proper divisors (19991).

81803509 is a wasteful number, since it uses less digits than its factorization.

81803509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19990.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 81803509 is about 9044.5292304243. The cubic root of 81803509 is about 434.1008582233.

The spelling of 81803509 in words is "eighty-one million, eight hundred three thousand, five hundred nine".