6721471921 has 4 divisors (see below), whose sum is σ = 6723569700. Its totient is φ = 6719374144.

The previous prime is 6721471919. The next prime is 6721471979. The reversal of 6721471921 is 1291741276.

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 5226567025 + 1494904896 = 72295^2 + 38664^2 .

It is a cyclic number.

It is not a de Polignac number, because 6721471921 - 2¹ = 6721471919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6721472921) 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, 1044076 + ... + 1050493.

It is an arithmetic number, because the mean of its divisors is an integer number (1680892425).

Almost surely, 2^6721471921 is an apocalyptic number.

It is an amenable number.

6721471921 is a deficient number, since it is larger than the sum of its proper divisors (2097779).

6721471921 is a wasteful number, since it uses less digits than its factorization.

6721471921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2097778.

The product of its digits is 42336, while the sum is 40.

The square root of 6721471921 is about 81984.5834349361. The cubic root of 6721471921 is about 1887.2153612913.

The spelling of 6721471921 in words is "six billion, seven hundred twenty-one million, four hundred seventy-one thousand, nine hundred twenty-one".