51666661 has 4 divisors (see below), whose sum is σ = 53448300. Its totient is φ = 49885024.

The previous prime is 51666649. The next prime is 51666707. The reversal of 51666661 is 16666615.

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 28569025 + 23097636 = 5345^2 + 4806^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51666661 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 51666661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51664661) 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, 890776 + ... + 890833.

It is an arithmetic number, because the mean of its divisors is an integer number (13362075).

Almost surely, 2^51666661 is an apocalyptic number.

It is an amenable number.

51666661 is a deficient number, since it is larger than the sum of its proper divisors (1781639).

51666661 is a wasteful number, since it uses less digits than its factorization.

51666661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1781638.

The product of its digits is 38880, while the sum is 37.

The square root of 51666661 is about 7187.9524901045. The cubic root of 51666661 is about 372.4518466950.

The spelling of 51666661 in words is "fifty-one million, six hundred sixty-six thousand, six hundred sixty-one".