51997840 has 80 divisors (see below), whose sum is σ = 125991936. Its totient is φ = 19942400.

The previous prime is 51997811. The next prime is 51997853. The reversal of 51997840 is 4879915.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

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, 272145 + ... + 272335.

Almost surely, 2^51997840 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 51997840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (62995968).

51997840 is an abundant number, since it is smaller than the sum of its proper divisors (73994096).

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

51997840 is a wasteful number, since it uses less digits than its factorization.

51997840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328 (or 322 counting only the distinct ones).

The product of its (nonzero) digits is 90720, while the sum is 43.

The square root of 51997840 is about 7210.9527803197. The cubic root of 51997840 is about 373.2459475178.

The spelling of 51997840 in words is "fifty-one million, nine hundred ninety-seven thousand, eight hundred forty".