51639720 has 256 divisors, whose sum is σ = 186624000. Its totient is φ = 11289600.

The previous prime is 51639719. The next prime is 51639737. The reversal of 51639720 is 2793615.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 727285 + ... + 727355.

It is an arithmetic number, because the mean of its divisors is an integer number (729000).

Almost surely, 2^51639720 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 51639720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93312000).

51639720 is an abundant number, since it is smaller than the sum of its proper divisors (134984280).

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

51639720 is a wasteful number, since it uses less digits than its factorization.

51639720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 140 counting only the distinct ones).

The product of its (nonzero) digits is 11340, while the sum is 33.

The square root of 51639720 is about 7186.0782072004. The cubic root of 51639720 is about 372.3870984957.

The spelling of 51639720 in words is "fifty-one million, six hundred thirty-nine thousand, seven hundred twenty".