65521 has 2 divisors, whose sum is σ = 65522.
Its totient is φ = 65520.
The previous prime is 65519. The next prime is 65537. The reversal of 65521 is 12556.
It is a happy number.
It is the 105-th star number.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 57600 + 7921 = 240^2 + 89^2
It is a cyclic number.
It is not a de Polignac number, because 65521 - 21 = 65519 is a prime.
Together with 65519, it forms a pair of twin primes.
It is a Chen prime.
65521 is a lucky number.
It is a nialpdrome in base 10 and base 16.
It is not a weakly prime, because it can be changed into another prime (65551) 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, 32760 + 32761.
It is an arithmetic number, because the mean of its divisors is an integer number (32761).
265521 is an apocalyptic number.
It is an amenable number.
65521 is a deficient number, since it is larger than the sum of its proper divisors (1).
65521 is an equidigital number, since it uses as much as digits as its factorization.
65521 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 300, while the sum is 19.
The square root of 65521 is about 255.9707014484.
The cubic root of 65521 is about 40.3143973828.
It can be divided in two parts, 655 and 21, that added together give a palindrome (676).
The spelling of 65521 in words is "sixty-five thousand, five hundred twenty-one".