6647521 has 2 divisors, whose sum is σ = 6647522. Its totient is φ = 6647520.

The previous prime is 6647519. The next prime is 6647551. The reversal of 6647521 is 1257466.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6431296 + 216225 = 2536^2 + 465^2 .

It is a cyclic number.

It is not a de Polignac number, because 6647521 - 2¹ = 6647519 is a prime.

Together with 6647519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (6647551) 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 as a sum of consecutive naturals, namely, 3323760 + 3323761.

It is an arithmetic number, because the mean of its divisors is an integer number (3323761).

Almost surely, 2^6647521 is an apocalyptic number.

It is an amenable number.

6647521 is a deficient number, since it is larger than the sum of its proper divisors (1).

6647521 is an equidigital number, since it uses as much as digits as its factorization.

6647521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10080, while the sum is 31.

The square root of 6647521 is about 2578.2786893585. The cubic root of 6647521 is about 188.0268654077.

The spelling of 6647521 in words is "six million, six hundred forty-seven thousand, five hundred twenty-one".