78643813 has 2 divisors, whose sum is σ = 78643814. Its totient is φ = 78643812.

The previous prime is 78643801. The next prime is 78643841. The reversal of 78643813 is 31834687.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77123524 + 1520289 = 8782^2 + 1233^2 .

It is an emirp because it is prime and its reverse (31834687) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78643813 - 2¹³ = 78635621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78643013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39321906 + 39321907.

It is an arithmetic number, because the mean of its divisors is an integer number (39321907).

Almost surely, 2^78643813 is an apocalyptic number.

It is an amenable number.

78643813 is a deficient number, since it is larger than the sum of its proper divisors (1).

78643813 is an equidigital number, since it uses as much as digits as its factorization.

78643813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 96768, while the sum is 40.

The square root of 78643813 is about 8868.1346967668. The cubic root of 78643813 is about 428.4382012289.

The spelling of 78643813 in words is "seventy-eight million, six hundred forty-three thousand, eight hundred thirteen".