51991728 has 80 divisors (see below), whose sum is σ = 138848256. Its totient is φ = 16756480.

The previous prime is 51991727. The next prime is 51991741. The reversal of 51991728 is 82719915.

It is a self number, because there is not a number n which added to its sum of digits gives 51991728.

It is not an unprimeable number, because it can be changed into a prime (51991721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 272113 + ... + 272303.

Almost surely, 2^51991728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 51991728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (69424128).

51991728 is an abundant number, since it is smaller than the sum of its proper divisors (86856528).

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

51991728 is a wasteful number, since it uses less digits than its factorization.

51991728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 362 (or 356 counting only the distinct ones).

The product of its digits is 45360, while the sum is 42.

The square root of 51991728 is about 7210.5289681132. The cubic root of 51991728 is about 373.2313227525.

The spelling of 51991728 in words is "fifty-one million, nine hundred ninety-one thousand, seven hundred twenty-eight".