6721501671221 has 4 divisors (see below), whose sum is σ = 6721581137772. Its totient is φ = 6721422204672.

The previous prime is 6721501671211. The next prime is 6721501671281. The reversal of 6721501671221 is 1221761051276.

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 5673857304196 + 1047644367025 = 2381986^2 + 1023545^2 .

It is a cyclic number.

It is not a de Polignac number, because 6721501671221 - 2¹⁰ = 6721501670197 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 (6721501671211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39606266 + ... + 39775611.

It is an arithmetic number, because the mean of its divisors is an integer number (1680395284443).

Almost surely, 2^{6721501671221} is an apocalyptic number.

It is an amenable number.

6721501671221 is a deficient number, since it is larger than the sum of its proper divisors (79466551).

6721501671221 is an equidigital number, since it uses as much as digits as its factorization.

6721501671221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79466550.

The product of its (nonzero) digits is 70560, while the sum is 41.

The spelling of 6721501671221 in words is "six trillion, seven hundred twenty-one billion, five hundred one million, six hundred seventy-one thousand, two hundred twenty-one".