6521378809 has 4 divisors (see below), whose sum is σ = 7114231440. Its totient is φ = 5928526180.

The previous prime is 6521378729. The next prime is 6521378813. The reversal of 6521378809 is 9088731256.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6521378809 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6521378849) 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, 296426299 + ... + 296426320.

It is an arithmetic number, because the mean of its divisors is an integer number (1778557860).

Almost surely, 2^6521378809 is an apocalyptic number.

It is an amenable number.

6521378809 is a deficient number, since it is larger than the sum of its proper divisors (592852631).

6521378809 is a wasteful number, since it uses less digits than its factorization.

6521378809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592852630.

The product of its (nonzero) digits is 725760, while the sum is 49.

The square root of 6521378809 is about 80755.0543867070. The cubic root of 6521378809 is about 1868.2994070659.

The spelling of 6521378809 in words is "six billion, five hundred twenty-one million, three hundred seventy-eight thousand, eight hundred nine".