51021720 has 96 divisors (see below), whose sum is σ = 166795200. Its totient is φ = 13526016.

The previous prime is 51021713. The next prime is 51021721. The reversal of 51021720 is 2712015.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 51021693 and 51021702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51021721) 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 23 ways as a sum of consecutive naturals, for example, 85744 + ... + 86336.

It is an arithmetic number, because the mean of its divisors is an integer number (1737450).

Almost surely, 2^51021720 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 51021720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (83397600).

51021720 is an abundant number, since it is smaller than the sum of its proper divisors (115773480).

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

51021720 is a wasteful number, since it uses less digits than its factorization.

51021720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 849 (or 842 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 51021720 is about 7142.9489708383. The cubic root of 51021720 is about 370.8956146147.

Adding to 51021720 its reverse (2712015), we get a palindrome (53733735).

The spelling of 51021720 in words is "fifty-one million, twenty-one thousand, seven hundred twenty".