6399521 has 2 divisors, whose sum is σ = 6399522. Its totient is φ = 6399520.

The previous prime is 6399511. The next prime is 6399527. The reversal of 6399521 is 1259936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5569600 + 829921 = 2360^2 + 911^2 .

It is a cyclic number.

It is not a de Polignac number, because 6399521 - 2⁶ = 6399457 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 (6399527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3199760 + 3199761.

It is an arithmetic number, because the mean of its divisors is an integer number (3199761).

Almost surely, 2^6399521 is an apocalyptic number.

It is an amenable number.

6399521 is a deficient number, since it is larger than the sum of its proper divisors (1).

6399521 is an equidigital number, since it uses as much as digits as its factorization.

6399521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14580, while the sum is 35.

The square root of 6399521 is about 2529.7274556758. The cubic root of 6399521 is about 185.6589213101.

The spelling of 6399521 in words is "six million, three hundred ninety-nine thousand, five hundred twenty-one".