6404921 has 2 divisors, whose sum is σ = 6404922. Its totient is φ = 6404920.

The previous prime is 6404917. The next prime is 6404927. The reversal of 6404921 is 1294046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5107600 + 1297321 = 2260^2 + 1139^2 .

It is a cyclic number.

It is not a de Polignac number, because 6404921 - 2² = 6404917 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (6404927) 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, 3202460 + 3202461.

It is an arithmetic number, because the mean of its divisors is an integer number (3202461).

Almost surely, 2^6404921 is an apocalyptic number.

It is an amenable number.

6404921 is a deficient number, since it is larger than the sum of its proper divisors (1).

6404921 is an equidigital number, since it uses as much as digits as its factorization.

6404921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 6404921 is about 2530.7945392702. The cubic root of 6404921 is about 185.7111271089.

Adding to 6404921 its reverse (1294046), we get a palindrome (7698967).

The spelling of 6404921 in words is "six million, four hundred four thousand, nine hundred twenty-one".