9978809 has 4 divisors (see below), whose sum is σ = 9985140. Its totient is φ = 9972480.

The previous prime is 9978799. The next prime is 9978811. The reversal of 9978809 is 9088799.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9088799 = 379 ⋅23981.

It can be written as a sum of positive squares in 2 ways, for example, as 2839225 + 7139584 = 1685^2 + 2672^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9978809 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9978889) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1289 + ... + 4649.

It is an arithmetic number, because the mean of its divisors is an integer number (2496285).

Almost surely, 2^9978809 is an apocalyptic number.

It is an amenable number.

9978809 is a deficient number, since it is larger than the sum of its proper divisors (6331).

9978809 is a wasteful number, since it uses less digits than its factorization.

9978809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6330.

The product of its (nonzero) digits is 326592, while the sum is 50.

The square root of 9978809 is about 3158.9252919308. The cubic root of 9978809 is about 215.2911792950.

The spelling of 9978809 in words is "nine million, nine hundred seventy-eight thousand, eight hundred nine".