78864221 has 2 divisors, whose sum is σ = 78864222. Its totient is φ = 78864220.

The previous prime is 78864161. The next prime is 78864223. The reversal of 78864221 is 12246887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78765625 + 98596 = 8875^2 + 314^2 .

It is a cyclic number.

It is not a de Polignac number, because 78864221 - 2⁶ = 78864157 is a prime.

Together with 78864223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78864223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39432110 + 39432111.

It is an arithmetic number, because the mean of its divisors is an integer number (39432111).

Almost surely, 2^78864221 is an apocalyptic number.

It is an amenable number.

78864221 is a deficient number, since it is larger than the sum of its proper divisors (1).

78864221 is an equidigital number, since it uses as much as digits as its factorization.

78864221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43008, while the sum is 38.

The square root of 78864221 is about 8880.5529670173. The cubic root of 78864221 is about 428.8380764070.

The spelling of 78864221 in words is "seventy-eight million, eight hundred sixty-four thousand, two hundred twenty-one".