78909217 has 2 divisors, whose sum is σ = 78909218. Its totient is φ = 78909216.

The previous prime is 78909199. The next prime is 78909221. The reversal of 78909217 is 71290987.

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., 75359761 + 3549456 = 8681^2 + 1884^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78909217 is a prime.

It is not a weakly prime, because it can be changed into another prime (78909247) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39454608 + 39454609.

It is an arithmetic number, because the mean of its divisors is an integer number (39454609).

Almost surely, 2^78909217 is an apocalyptic number.

It is an amenable number.

78909217 is a deficient number, since it is larger than the sum of its proper divisors (1).

78909217 is an equidigital number, since it uses as much as digits as its factorization.

78909217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 78909217 is about 8883.0860065633. The cubic root of 78909217 is about 428.9196187897.

The spelling of 78909217 in words is "seventy-eight million, nine hundred nine thousand, two hundred seventeen".