51811920 has 240 divisors, whose sum is σ = 191862720. Its totient is φ = 12847104.

The previous prime is 51811901. The next prime is 51811927. The reversal of 51811920 is 2911815.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51811927) 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 47 ways as a sum of consecutive naturals, for example, 624199 + ... + 624281.

It is an arithmetic number, because the mean of its divisors is an integer number (799428).

Almost surely, 2^51811920 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 51811920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95931360).

51811920 is an abundant number, since it is smaller than the sum of its proper divisors (140050800).

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

51811920 is a wasteful number, since it uses less digits than its factorization.

51811920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139 (or 110 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 27.

The square root of 51811920 is about 7198.0497358660. The cubic root of 51811920 is about 372.8005651842.

The spelling of 51811920 in words is "fifty-one million, eight hundred eleven thousand, nine hundred twenty".