78612221 has 2 divisors, whose sum is σ = 78612222. Its totient is φ = 78612220.

The previous prime is 78612203. The next prime is 78612223. The reversal of 78612221 is 12221687.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70375321 + 8236900 = 8389^2 + 2870^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78612221 is a prime.

It is a Sophie Germain prime.

Together with 78612223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78612223) 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, 39306110 + 39306111.

It is an arithmetic number, because the mean of its divisors is an integer number (39306111).

Almost surely, 2^78612221 is an apocalyptic number.

It is an amenable number.

78612221 is a deficient number, since it is larger than the sum of its proper divisors (1).

78612221 is an equidigital number, since it uses as much as digits as its factorization.

78612221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 29.

The square root of 78612221 is about 8866.3533089991. The cubic root of 78612221 is about 428.3808242531.

The spelling of 78612221 in words is "seventy-eight million, six hundred twelve thousand, two hundred twenty-one".