51311440 has 80 divisors (see below), whose sum is σ = 130772880. Its totient is φ = 18636800.

The previous prime is 51311401. The next prime is 51311441. The reversal of 51311440 is 4411315.

51311440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 8 ways, for example, as 4032064 + 47279376 = 2008^2 + 6876^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51311441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38790 + ... + 40090.

It is an arithmetic number, because the mean of its divisors is an integer number (1634661).

Almost surely, 2^51311440 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 51311440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (65386440).

51311440 is an abundant number, since it is smaller than the sum of its proper divisors (79461440).

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

51311440 is a wasteful number, since it uses less digits than its factorization.

51311440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1360 (or 1354 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 51311440 is about 7163.2004020549. The cubic root of 51311440 is about 371.5963170176.

Adding to 51311440 its reverse (4411315), we get a palindrome (55722755).

The spelling of 51311440 in words is "fifty-one million, three hundred eleven thousand, four hundred forty".