78785821 has 2 divisors, whose sum is σ = 78785822. Its totient is φ = 78785820.

The previous prime is 78785813. The next prime is 78785843. The reversal of 78785821 is 12858787.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56460196 + 22325625 = 7514^2 + 4725^2 .

It is an emirp because it is prime and its reverse (12858787) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78785821 - 2³ = 78785813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78785801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39392910 + 39392911.

It is an arithmetic number, because the mean of its divisors is an integer number (39392911).

Almost surely, 2^78785821 is an apocalyptic number.

It is an amenable number.

78785821 is a deficient number, since it is larger than the sum of its proper divisors (1).

78785821 is an equidigital number, since it uses as much as digits as its factorization.

78785821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 250880, while the sum is 46.

The square root of 78785821 is about 8876.1377298913. The cubic root of 78785821 is about 428.6959246939.

The spelling of 78785821 in words is "seventy-eight million, seven hundred eighty-five thousand, eight hundred twenty-one".