666608021701 has 4 divisors (see below), whose sum is σ = 688111506304. Its totient is φ = 645104537100.

The previous prime is 666608021687. The next prime is 666608021711. The reversal of 666608021701 is 107120806666.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 107120806666 = 2 ⋅53560403333.

It is a cyclic number.

It is not a de Polignac number, because 666608021701 - 2⁵ = 666608021669 is a prime.

It is a super-2 number, since 2×666608021701² (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 (666608021711) 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, 10751742255 + ... + 10751742316.

It is an arithmetic number, because the mean of its divisors is an integer number (172027876576).

Almost surely, 2^666608021701 is an apocalyptic number.

It is an amenable number.

666608021701 is a deficient number, since it is larger than the sum of its proper divisors (21503484603).

666608021701 is a wasteful number, since it uses less digits than its factorization.

666608021701 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21503484602.

The product of its (nonzero) digits is 145152, while the sum is 43.

The spelling of 666608021701 in words is "six hundred sixty-six billion, six hundred eight million, twenty-one thousand, seven hundred one".