78191321 has 4 divisors (see below), whose sum is σ = 84206052. Its totient is φ = 72176592.

The previous prime is 78191303. The next prime is 78191339. The reversal of 78191321 is 12319187.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12319187 = 37 ⋅332951.

It is an interprime number because it is at equal distance from previous prime (78191303) and next prime (78191339).

It can be written as a sum of positive squares in 2 ways, for example, as 26925721 + 51265600 = 5189^2 + 7160^2 .

It is a cyclic number.

It is not a de Polignac number, because 78191321 - 2⁶ = 78191257 is a prime.

It is a super-2 number, since 2×78191321² = 12227765359450082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78191371) 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 in 3 ways as a sum of consecutive naturals, for example, 3007346 + ... + 3007371.

It is an arithmetic number, because the mean of its divisors is an integer number (21051513).

Almost surely, 2^78191321 is an apocalyptic number.

It is an amenable number.

78191321 is a deficient number, since it is larger than the sum of its proper divisors (6014731).

78191321 is a wasteful number, since it uses less digits than its factorization.

78191321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6014730.

The product of its digits is 3024, while the sum is 32.

The square root of 78191321 is about 8842.5856512674. The cubic root of 78191321 is about 427.6149202575.

The spelling of 78191321 in words is "seventy-eight million, one hundred ninety-one thousand, three hundred twenty-one".