51251640 has 128 divisors (see below), whose sum is σ = 172005120. Its totient is φ = 12108800.

The previous prime is 51251639. The next prime is 51251647. The reversal of 51251640 is 4615215.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 51251640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51251647) 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 31 ways as a sum of consecutive naturals, for example, 53647 + ... + 54593.

It is an arithmetic number, because the mean of its divisors is an integer number (1343790).

Almost surely, 2^51251640 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 51251640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (86002560).

51251640 is an abundant number, since it is smaller than the sum of its proper divisors (120753480).

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

51251640 is a wasteful number, since it uses less digits than its factorization.

51251640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1013 (or 1009 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 51251640 is about 7159.0250732904. The cubic root of 51251640 is about 371.4519041414.

Adding to 51251640 its reverse (4615215), we get a palindrome (55866855).

The spelling of 51251640 in words is "fifty-one million, two hundred fifty-one thousand, six hundred forty".