78777221 has 2 divisors, whose sum is σ = 78777222. Its totient is φ = 78777220.

The previous prime is 78777199. The next prime is 78777241. The reversal of 78777221 is 12277787.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 75446596 + 3330625 = 8686^2 + 1825^2 .

It is a cyclic number.

It is not a de Polignac number, because 78777221 - 2⁶ = 78777157 is a prime.

It is a Sophie Germain prime.

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 (78777241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39388610 + 39388611.

It is an arithmetic number, because the mean of its divisors is an integer number (39388611).

Almost surely, 2^78777221 is an apocalyptic number.

It is an amenable number.

78777221 is a deficient number, since it is larger than the sum of its proper divisors (1).

78777221 is an equidigital number, since it uses as much as digits as its factorization.

78777221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 76832, while the sum is 41.

The square root of 78777221 is about 8875.6532717316. The cubic root of 78777221 is about 428.6803257826.

The spelling of 78777221 in words is "seventy-eight million, seven hundred seventy-seven thousand, two hundred twenty-one".