6646921 has 2 divisors, whose sum is σ = 6646922. Its totient is φ = 6646920.

The previous prime is 6646919. The next prime is 6646933. The reversal of 6646921 is 1296466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4862025 + 1784896 = 2205^2 + 1336^2 .

It is a cyclic number.

It is not a de Polignac number, because 6646921 - 2¹ = 6646919 is a prime.

Together with 6646919, it forms a pair of twin primes.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (6646951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3323460 + 3323461.

It is an arithmetic number, because the mean of its divisors is an integer number (3323461).

Almost surely, 2^6646921 is an apocalyptic number.

It is an amenable number.

6646921 is a deficient number, since it is larger than the sum of its proper divisors (1).

6646921 is an equidigital number, since it uses as much as digits as its factorization.

6646921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 34.

The square root of 6646921 is about 2578.1623300328. The cubic root of 6646921 is about 188.0212081854.

The spelling of 6646921 in words is "six million, six hundred forty-six thousand, nine hundred twenty-one".