51666665 has 4 divisors (see below), whose sum is σ = 62000004. Its totient is φ = 41333328.

The previous prime is 51666649. The next prime is 51666707. The reversal of 51666665 is 56666615.

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 14077504 + 37589161 = 3752^2 + 6131^2 .

It is a cyclic number.

It is not a de Polignac number, because 51666665 - 2⁴ = 51666649 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5166662 + ... + 5166671.

It is an arithmetic number, because the mean of its divisors is an integer number (15500001).

Almost surely, 2^51666665 is an apocalyptic number.

It is an amenable number.

51666665 is a deficient number, since it is larger than the sum of its proper divisors (10333339).

51666665 is a wasteful number, since it uses less digits than its factorization.

51666665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10333338.

The product of its digits is 194400, while the sum is 41.

The square root of 51666665 is about 7187.9527683479. The cubic root of 51666665 is about 372.4518563067.

The spelling of 51666665 in words is "fifty-one million, six hundred sixty-six thousand, six hundred sixty-five".