78208391 has 2 divisors, whose sum is σ = 78208392. Its totient is φ = 78208390.

The previous prime is 78208373. The next prime is 78208397. The reversal of 78208391 is 19380287.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78208391 - 2²⁶ = 11099527 is a prime.

It is a super-2 number, since 2×78208391² = 12233104845617762, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78208397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39104195 + 39104196.

It is an arithmetic number, because the mean of its divisors is an integer number (39104196).

Almost surely, 2^78208391 is an apocalyptic number.

78208391 is a deficient number, since it is larger than the sum of its proper divisors (1).

78208391 is an equidigital number, since it uses as much as digits as its factorization.

78208391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 78208391 is about 8843.5508140113. The cubic root of 78208391 is about 427.6460356272.

The spelling of 78208391 in words is "seventy-eight million, two hundred eight thousand, three hundred ninety-one".