6543721 has 4 divisors (see below), whose sum is σ = 6550672. Its totient is φ = 6536772.

The previous prime is 6543701. The next prime is 6543731. The reversal of 6543721 is 1273456.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 6543721 - 2¹⁵ = 6510953 is a prime.

It is a Duffinian number.

6543721 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 6543721.

It is not an unprimeable number, because it can be changed into a prime (6543701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1791 + ... + 4036.

It is an arithmetic number, because the mean of its divisors is an integer number (1637668).

Almost surely, 2^6543721 is an apocalyptic number.

It is an amenable number.

6543721 is a deficient number, since it is larger than the sum of its proper divisors (6951).

6543721 is a wasteful number, since it uses less digits than its factorization.

6543721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6950.

The product of its digits is 5040, while the sum is 28.

The square root of 6543721 is about 2558.0697801272. The cubic root of 6543721 is about 187.0430568016.

The spelling of 6543721 in words is "six million, five hundred forty-three thousand, seven hundred twenty-one".