78870221 has 2 divisors, whose sum is σ = 78870222. Its totient is φ = 78870220.

The previous prime is 78870217. The next prime is 78870223. The reversal of 78870221 is 12207887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43705321 + 35164900 = 6611^2 + 5930^2 .

It is a cyclic number.

It is not a de Polignac number, because 78870221 - 2² = 78870217 is a prime.

Together with 78870223, 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 (78870223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39435110 + 39435111.

It is an arithmetic number, because the mean of its divisors is an integer number (39435111).

Almost surely, 2^78870221 is an apocalyptic number.

It is an amenable number.

78870221 is a deficient number, since it is larger than the sum of its proper divisors (1).

78870221 is an equidigital number, since it uses as much as digits as its factorization.

78870221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 78870221 is about 8880.8907773939. The cubic root of 78870221 is about 428.8489514831.

The spelling of 78870221 in words is "seventy-eight million, eight hundred seventy thousand, two hundred twenty-one".