6540579821 has 4 divisors (see below), whose sum is σ = 6543789600. Its totient is φ = 6537370044.

The previous prime is 6540579811. The next prime is 6540579863. The reversal of 6540579821 is 1289750456.

It is a happy number.

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-6540579821 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 (6540579811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1601831 + ... + 1605908.

It is an arithmetic number, because the mean of its divisors is an integer number (1635947400).

Almost surely, 2^6540579821 is an apocalyptic number.

It is an amenable number.

6540579821 is a deficient number, since it is larger than the sum of its proper divisors (3209779).

6540579821 is a wasteful number, since it uses less digits than its factorization.

6540579821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3209778.

The product of its (nonzero) digits is 604800, while the sum is 47.

The square root of 6540579821 is about 80873.8512808683. The cubic root of 6540579821 is about 1870.1312328426.

The spelling of 6540579821 in words is "six billion, five hundred forty million, five hundred seventy-nine thousand, eight hundred twenty-one".