51505661664 has 36 divisors (see below), whose sum is σ = 146469226176. Its totient is φ = 17168553792.

The previous prime is 51505661659. The next prime is 51505661677. The reversal of 51505661664 is 46616650515.

51505661664 is a `hidden beast` number, since 5 + 15 + 0 + 566 + 16 + 64 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 89419264 + ... + 89419839.

It is an arithmetic number, because the mean of its divisors is an integer number (4068589616).

Almost surely, 2^51505661664 is an apocalyptic number.

It is an amenable number.

51505661664 is an abundant number, since it is smaller than the sum of its proper divisors (94963564512).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51505661664 is a wasteful number, since it uses less digits than its factorization.

51505661664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178839119 (or 178839108 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 45.

The spelling of 51505661664 in words is "fifty-one billion, five hundred five million, six hundred sixty-one thousand, six hundred sixty-four".