78516209 has 2 divisors, whose sum is σ = 78516210. Its totient is φ = 78516208.

The previous prime is 78516203. The next prime is 78516233. The reversal of 78516209 is 90261587.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65157184 + 13359025 = 8072^2 + 3655^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78516209 is a prime.

It is not a weakly prime, because it can be changed into another prime (78516203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39258104 + 39258105.

It is an arithmetic number, because the mean of its divisors is an integer number (39258105).

Almost surely, 2^78516209 is an apocalyptic number.

It is an amenable number.

78516209 is a deficient number, since it is larger than the sum of its proper divisors (1).

78516209 is an equidigital number, since it uses as much as digits as its factorization.

78516209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 78516209 is about 8860.9372529095. The cubic root of 78516209 is about 428.2063541137.

The spelling of 78516209 in words is "seventy-eight million, five hundred sixteen thousand, two hundred nine".