51991808 has 72 divisors (see below), whose sum is σ = 116508000. Its totient is φ = 22947840.

The previous prime is 51991783. The next prime is 51991843. The reversal of 51991808 is 80819915.

It is a congruent number.

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, 103943 + ... + 104441.

Almost surely, 2^51991808 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 51991808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (58254000).

51991808 is an abundant number, since it is smaller than the sum of its proper divisors (64516192).

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

51991808 is a wasteful number, since it uses less digits than its factorization.

51991808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 563 (or 549 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 41.

The square root of 51991808 is about 7210.5345155543. The cubic root of 51991808 is about 373.2315141835.

It can be divided in two parts, 5199 and 1808, that added together give a palindrome (7007).

The spelling of 51991808 in words is "fifty-one million, nine hundred ninety-one thousand, eight hundred eight".