66637718617 has 4 divisors (see below), whose sum is σ = 70557584436. Its totient is φ = 62717852800.

The previous prime is 66637718603. The next prime is 66637718621. The reversal of 66637718617 is 71681773666.

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 36299394576 + 30338324041 = 190524^2 + 174179^2 .

It is a cyclic number.

It is not a de Polignac number, because 66637718617 - 2⁷ = 66637718489 is a prime.

It is a super-3 number, since 3×66637718617³ (a number of 33 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66637718677) 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, 1959932884 + ... + 1959932917.

It is an arithmetic number, because the mean of its divisors is an integer number (17639396109).

Almost surely, 2^66637718617 is an apocalyptic number.

It is an amenable number.

66637718617 is a deficient number, since it is larger than the sum of its proper divisors (3919865819).

66637718617 is a wasteful number, since it uses less digits than its factorization.

66637718617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3919865818.

The product of its digits is 10668672, while the sum is 58.

The spelling of 66637718617 in words is "sixty-six billion, six hundred thirty-seven million, seven hundred eighteen thousand, six hundred seventeen".