81241609 has 2 divisors, whose sum is σ = 81241610. Its totient is φ = 81241608.

The previous prime is 81241583. The next prime is 81241619. The reversal of 81241609 is 90614218.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 49070025 + 32171584 = 7005^2 + 5672^2 .

It is a cyclic number.

It is not a de Polignac number, because 81241609 - 2¹⁷ = 81110537 is a prime.

It is not a weakly prime, because it can be changed into another prime (81241619) 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 as a sum of consecutive naturals, namely, 40620804 + 40620805.

It is an arithmetic number, because the mean of its divisors is an integer number (40620805).

Almost surely, 2^81241609 is an apocalyptic number.

It is an amenable number.

81241609 is a deficient number, since it is larger than the sum of its proper divisors (1).

81241609 is an equidigital number, since it uses as much as digits as its factorization.

81241609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 81241609 is about 9013.4127277075. The cubic root of 81241609 is about 433.1046421831.

The spelling of 81241609 in words is "eighty-one million, two hundred forty-one thousand, six hundred nine".