81550289 has 2 divisors, whose sum is σ = 81550290. Its totient is φ = 81550288.

The previous prime is 81550283. The next prime is 81550307. The reversal of 81550289 is 98205518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 59413264 + 22137025 = 7708^2 + 4705^2 .

It is a cyclic number.

It is not a de Polignac number, because 81550289 - 2¹² = 81546193 is a prime.

It is not a weakly prime, because it can be changed into another prime (81550283) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40775144 + 40775145.

It is an arithmetic number, because the mean of its divisors is an integer number (40775145).

Almost surely, 2^81550289 is an apocalyptic number.

It is an amenable number.

81550289 is a deficient number, since it is larger than the sum of its proper divisors (1).

81550289 is an equidigital number, since it uses as much as digits as its factorization.

81550289 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 28800, while the sum is 38.

The square root of 81550289 is about 9030.5198632194. The cubic root of 81550289 is about 433.6524804087.

The spelling of 81550289 in words is "eighty-one million, five hundred fifty thousand, two hundred eighty-nine".