668510665261 has 4 divisors (see below), whose sum is σ = 668554774524. Its totient is φ = 668466556000.

The previous prime is 668510665237. The next prime is 668510665267. The reversal of 668510665261 is 162566015866.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 162566015866 = 2 ⋅81283007933.

It can be written as a sum of positive squares in 2 ways, for example, as 332215057161 + 336295608100 = 576381^2 + 579910^2 .

It is a cyclic number.

It is not a de Polignac number, because 668510665261 - 2¹³ = 668510657069 is a prime.

It is a super-3 number, since 3×668510665261³ (a number of 36 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 668510665199 and 668510665208.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668510665267) 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, 22031890 + ... + 22062211.

It is an arithmetic number, because the mean of its divisors is an integer number (167138693631).

Almost surely, 2^668510665261 is an apocalyptic number.

It is an amenable number.

668510665261 is a deficient number, since it is larger than the sum of its proper divisors (44109263).

668510665261 is a wasteful number, since it uses less digits than its factorization.

668510665261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44109262.

The product of its (nonzero) digits is 3110400, while the sum is 52.

The spelling of 668510665261 in words is "six hundred sixty-eight billion, five hundred ten million, six hundred sixty-five thousand, two hundred sixty-one".