78578221 has 2 divisors, whose sum is σ = 78578222. Its totient is φ = 78578220.

The previous prime is 78578207. The next prime is 78578237. The reversal of 78578221 is 12287587.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69122596 + 9455625 = 8314^2 + 3075^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78578221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78578251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39289110 + 39289111.

It is an arithmetic number, because the mean of its divisors is an integer number (39289111).

Almost surely, 2^78578221 is an apocalyptic number.

It is an amenable number.

78578221 is a deficient number, since it is larger than the sum of its proper divisors (1).

78578221 is an equidigital number, since it uses as much as digits as its factorization.

78578221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62720, while the sum is 40.

The square root of 78578221 is about 8864.4357406436. The cubic root of 78578221 is about 428.3190567224.

The spelling of 78578221 in words is "seventy-eight million, five hundred seventy-eight thousand, two hundred twenty-one".