78745965821 has 2 divisors, whose sum is σ = 78745965822. Its totient is φ = 78745965820.

The previous prime is 78745965817. The next prime is 78745965847. The reversal of 78745965821 is 12856954787.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 71187576100 + 7558389721 = 266810^2 + 86939^2 .

It is a cyclic number.

It is not a de Polignac number, because 78745965821 - 2² = 78745965817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78745965871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39372982910 + 39372982911.

It is an arithmetic number, because the mean of its divisors is an integer number (39372982911).

Almost surely, 2^78745965821 is an apocalyptic number.

It is an amenable number.

78745965821 is a deficient number, since it is larger than the sum of its proper divisors (1).

78745965821 is an equidigital number, since it uses as much as digits as its factorization.

78745965821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 33868800, while the sum is 62.

The spelling of 78745965821 in words is "seventy-eight billion, seven hundred forty-five million, nine hundred sixty-five thousand, eight hundred twenty-one".