51666616661 has 16 divisors (see below), whose sum is σ = 56683019328. Its totient is φ = 46703692800.

The previous prime is 51666616649. The next prime is 51666616667. The reversal of 51666616661 is 16661666615.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 51666616661 - 2²⁶ = 51599507797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51666616667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5678726 + ... + 5687816.

It is an arithmetic number, because the mean of its divisors is an integer number (3542688708).

Almost surely, 2^51666616661 is an apocalyptic number.

It is an amenable number.

51666616661 is a deficient number, since it is larger than the sum of its proper divisors (5016402667).

51666616661 is a wasteful number, since it uses less digits than its factorization.

51666616661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11972.

The product of its digits is 1399680, while the sum is 50.

The spelling of 51666616661 in words is "fifty-one billion, six hundred sixty-six million, six hundred sixteen thousand, six hundred sixty-one".