51720816 has 80 divisors (see below), whose sum is σ = 155347200. Its totient is φ = 14521344.

The previous prime is 51720811. The next prime is 51720829. The reversal of 51720816 is 61802715.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51720811) 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 15 ways as a sum of consecutive naturals, for example, 18520 + ... + 21128.

It is an arithmetic number, because the mean of its divisors is an integer number (1941840).

Almost surely, 2^51720816 is an apocalyptic number.

51720816 is a gapful number since it is divisible by the number (56) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 51720816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (77673600).

51720816 is an abundant number, since it is smaller than the sum of its proper divisors (103626384).

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

51720816 is a wasteful number, since it uses less digits than its factorization.

51720816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2686 (or 2680 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 51720816 is about 7191.7185706895. The cubic root of 51720816 is about 372.5819311394.

The spelling of 51720816 in words is "fifty-one million, seven hundred twenty thousand, eight hundred sixteen".