6519978385 has 4 divisors (see below), whose sum is σ = 7823974068. Its totient is φ = 5215982704.

The previous prime is 6519978379. The next prime is 6519978403. The reversal of 6519978385 is 5838799156.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3039096384 + 3480882001 = 55128^2 + 58999^2 .

It is a cyclic number.

It is not a de Polignac number, because 6519978385 - 2⁹ = 6519977873 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 651997834 + ... + 651997843.

It is an arithmetic number, because the mean of its divisors is an integer number (1955993517).

Almost surely, 2^6519978385 is an apocalyptic number.

It is an amenable number.

6519978385 is a deficient number, since it is larger than the sum of its proper divisors (1303995683).

6519978385 is a wasteful number, since it uses less digits than its factorization.

6519978385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1303995682.

The product of its digits is 16329600, while the sum is 61.

The square root of 6519978385 is about 80746.3831078520. The cubic root of 6519978385 is about 1868.1656624130.

The spelling of 6519978385 in words is "six billion, five hundred nineteen million, nine hundred seventy-eight thousand, three hundred eighty-five".