666611021517 has 64 divisors (see below), whose sum is σ = 1046904090624. Its totient is φ = 369453934080.

The previous prime is 666611021473. The next prime is 666611021519. The reversal of 666611021517 is 715120116666.

It is a happy number.

It is not a de Polignac number, because 666611021517 - 2⁷ = 666611021389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666611021519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 43202958 + ... + 43218384.

It is an arithmetic number, because the mean of its divisors is an integer number (16357876416).

Almost surely, 2^666611021517 is an apocalyptic number.

It is an amenable number.

666611021517 is a deficient number, since it is larger than the sum of its proper divisors (380293069107).

666611021517 is a wasteful number, since it uses less digits than its factorization.

666611021517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15978.

The product of its (nonzero) digits is 90720, while the sum is 42.

The spelling of 666611021517 in words is "six hundred sixty-six billion, six hundred eleven million, twenty-one thousand, five hundred seventeen".