666343526521 has 4 divisors (see below), whose sum is σ = 666408400372. Its totient is φ = 666278652672.

The previous prime is 666343526503. The next prime is 666343526531. The reversal of 666343526521 is 125625343666.

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 318249426496 + 348094100025 = 564136^2 + 589995^2 .

It is a cyclic number.

It is not a de Polignac number, because 666343526521 - 2⁷ = 666343526393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666343526531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32421516 + ... + 32442061.

It is an arithmetic number, because the mean of its divisors is an integer number (166602100093).

Almost surely, 2^666343526521 is an apocalyptic number.

It is an amenable number.

666343526521 is a deficient number, since it is larger than the sum of its proper divisors (64873851).

666343526521 is a wasteful number, since it uses less digits than its factorization.

666343526521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64873850.

The product of its digits is 4665600, while the sum is 49.

The spelling of 666343526521 in words is "six hundred sixty-six billion, three hundred forty-three million, five hundred twenty-six thousand, five hundred twenty-one".