51505661665 has 8 divisors (see below), whose sum is σ = 61811404200. Its totient is φ = 41201455872.

The previous prime is 51505661659. The next prime is 51505661677. The reversal of 51505661665 is 56616650515.

It can be written as a sum of positive squares in 4 ways, for example, as 8048422369 + 43457239296 = 89713^2 + 208464^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 51505661665 - 2⁹ = 51505661153 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 309114 + ... + 445603.

It is an arithmetic number, because the mean of its divisors is an integer number (7726425525).

Almost surely, 2^51505661665 is an apocalyptic number.

It is an amenable number.

51505661665 is a deficient number, since it is larger than the sum of its proper divisors (10305742535).

51505661665 is a wasteful number, since it uses less digits than its factorization.

51505661665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 768371.

The product of its (nonzero) digits is 810000, while the sum is 46.

The spelling of 51505661665 in words is "fifty-one billion, five hundred five million, six hundred sixty-one thousand, six hundred sixty-five".