78765221 has 2 divisors, whose sum is σ = 78765222. Its totient is φ = 78765220.

The previous prime is 78765209. The next prime is 78765251. The reversal of 78765221 is 12256787.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76912900 + 1852321 = 8770^2 + 1361^2 .

It is an emirp because it is prime and its reverse (12256787) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78765221 - 2¹⁰ = 78764197 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78765251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39382610 + 39382611.

It is an arithmetic number, because the mean of its divisors is an integer number (39382611).

Almost surely, 2^78765221 is an apocalyptic number.

It is an amenable number.

78765221 is a deficient number, since it is larger than the sum of its proper divisors (1).

78765221 is an equidigital number, since it uses as much as digits as its factorization.

78765221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 47040, while the sum is 38.

The square root of 78765221 is about 8874.9772394074. The cubic root of 78765221 is about 428.6585579625.

The spelling of 78765221 in words is "seventy-eight million, seven hundred sixty-five thousand, two hundred twenty-one".