78809819 has 4 divisors (see below), whose sum is σ = 85974360. Its totient is φ = 71645280.

The previous prime is 78809789. The next prime is 78809833. The reversal of 78809819 is 91890887.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 91890887 = 11 ⋅8353717.

It is a cyclic number.

It is not a de Polignac number, because 78809819 - 2¹⁶ = 78744283 is a prime.

It is a super-2 number, since 2×78809819² = 12421975141625522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78809839) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3582254 + ... + 3582275.

It is an arithmetic number, because the mean of its divisors is an integer number (21493590).

Almost surely, 2^78809819 is an apocalyptic number.

78809819 is a deficient number, since it is larger than the sum of its proper divisors (7164541).

78809819 is a wasteful number, since it uses less digits than its factorization.

78809819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7164540.

The product of its (nonzero) digits is 290304, while the sum is 50.

The square root of 78809819 is about 8877.4894536688. The cubic root of 78809819 is about 428.7394469094.

The spelling of 78809819 in words is "seventy-eight million, eight hundred nine thousand, eight hundred nineteen".