666638091517 has 4 divisors (see below), whose sum is σ = 701724306880. Its totient is φ = 631551876156.

The previous prime is 666638091463. The next prime is 666638091563. The reversal of 666638091517 is 715190836666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 666638091517 - 2¹⁹ = 666637567229 is a prime.

It is a super-2 number, since 2×666638091517² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666638092517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17543107653 + ... + 17543107690.

It is an arithmetic number, because the mean of its divisors is an integer number (175431076720).

Almost surely, 2^666638091517 is an apocalyptic number.

It is an amenable number.

666638091517 is a deficient number, since it is larger than the sum of its proper divisors (35086215363).

666638091517 is a wasteful number, since it uses less digits than its factorization.

666638091517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35086215362.

The product of its (nonzero) digits is 9797760, while the sum is 58.

The spelling of 666638091517 in words is "six hundred sixty-six billion, six hundred thirty-eight million, ninety-one thousand, five hundred seventeen".