81730309 has 2 divisors, whose sum is σ = 81730310. Its totient is φ = 81730308.

The previous prime is 81730307. The next prime is 81730331. The reversal of 81730309 is 90303718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 68062500 + 13667809 = 8250^2 + 3697^2 .

It is a cyclic number.

It is not a de Polignac number, because 81730309 - 2¹ = 81730307 is a prime.

Together with 81730307, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81730303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40865154 + 40865155.

It is an arithmetic number, because the mean of its divisors is an integer number (40865155).

Almost surely, 2^81730309 is an apocalyptic number.

It is an amenable number.

81730309 is a deficient number, since it is larger than the sum of its proper divisors (1).

81730309 is an equidigital number, since it uses as much as digits as its factorization.

81730309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 31.

The square root of 81730309 is about 9040.4816796452. The cubic root of 81730309 is about 433.9713378397.

The spelling of 81730309 in words is "eighty-one million, seven hundred thirty thousand, three hundred nine".