66317521 has 4 divisors (see below), whose sum is σ = 66350692. Its totient is φ = 66284352.

The previous prime is 66317497. The next prime is 66317557. The reversal of 66317521 is 12571366.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20349121 + 45968400 = 4511^2 + 6780^2 .

It is a cyclic number.

It is not a de Polignac number, because 66317521 - 2⁷ = 66317393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66317021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13380 + ... + 17653.

It is an arithmetic number, because the mean of its divisors is an integer number (16587673).

Almost surely, 2^66317521 is an apocalyptic number.

It is an amenable number.

66317521 is a deficient number, since it is larger than the sum of its proper divisors (33171).

66317521 is a wasteful number, since it uses less digits than its factorization.

66317521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33170.

The product of its digits is 7560, while the sum is 31.

The square root of 66317521 is about 8143.5570238072. The cubic root of 66317521 is about 404.7710355453.

Adding to 66317521 its reverse (12571366), we get a palindrome (78888887).

The spelling of 66317521 in words is "sixty-six million, three hundred seventeen thousand, five hundred twenty-one".