6521 has 2 divisors, whose sum is σ = 6522. Its totient is φ = 6520.

The previous prime is 6491. The next prime is 6529. The reversal of 6521 is 1256.

6521 is nontrivially palindromic in base 6.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6400 + 121 = 80^2 + 11^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6521 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a plaindrome in base 11.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 6496 and 6505.

It is not a weakly prime, because it can be changed into another prime (6529) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3260 + 3261.

It is an arithmetic number, because the mean of its divisors is an integer number (3261).

2⁶⁵²¹ is an apocalyptic number.

It is an amenable number.

6521 is a deficient number, since it is larger than the sum of its proper divisors (1).

6521 is an equidigital number, since it uses as much as digits as its factorization.

6521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60, while the sum is 14.

The square root of 6521 is about 80.7527089329. The cubic root of 6521 is about 18.6826323157.

Adding to 6521 its reverse (1256), we get a palindrome (7777).

The spelling of 6521 in words is "six thousand, five hundred twenty-one".