81820289 has 6 divisors (see below), whose sum is σ = 86353650. Its totient is φ = 77513616.

The previous prime is 81820259. The next prime is 81820309. The reversal of 81820289 is 98202818.

It can be written as a sum of positive squares in only one way, i.e., 81450625 + 369664 = 9025^2 + 608^2 .

It is not a de Polignac number, because 81820289 - 2⁸ = 81820033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81820229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 112964 + ... + 113685.

It is an arithmetic number, because the mean of its divisors is an integer number (14392275).

Almost surely, 2^81820289 is an apocalyptic number.

It is an amenable number.

81820289 is a deficient number, since it is larger than the sum of its proper divisors (4533361).

81820289 is a wasteful number, since it uses less digits than its factorization.

81820289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 226687 (or 226668 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 38.

The square root of 81820289 is about 9045.4568154406. The cubic root of 81820289 is about 434.1305379379.

The spelling of 81820289 in words is "eighty-one million, eight hundred twenty thousand, two hundred eighty-nine".