68540209 has 4 divisors (see below), whose sum is σ = 72572004. Its totient is φ = 64508416.

The previous prime is 68540203. The next prime is 68540221. The reversal of 68540209 is 90204586.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90204586 = 2 ⋅45102293.

It can be written as a sum of positive squares in 2 ways, for example, as 35224225 + 33315984 = 5935^2 + 5772^2 .

It is a cyclic number.

It is not a de Polignac number, because 68540209 - 2⁷ = 68540081 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (68540203) 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, 2015872 + ... + 2015905.

It is an arithmetic number, because the mean of its divisors is an integer number (18143001).

Almost surely, 2^68540209 is an apocalyptic number.

It is an amenable number.

68540209 is a deficient number, since it is larger than the sum of its proper divisors (4031795).

68540209 is a wasteful number, since it uses less digits than its factorization.

68540209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4031794.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 68540209 is about 8278.9014367850. The cubic root of 68540209 is about 409.2435168447.

The spelling of 68540209 in words is "sixty-eight million, five hundred forty thousand, two hundred nine".