51639840 has 288 divisors, whose sum is σ = 207567360. Its totient is φ = 11446272.

The previous prime is 51639839. The next prime is 51639877. The reversal of 51639840 is 4893615.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 51639795 and 51639804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 473706 + ... + 473814.

It is an arithmetic number, because the mean of its divisors is an integer number (720720).

Almost surely, 2^51639840 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 51639840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103783680).

51639840 is an abundant number, since it is smaller than the sum of its proper divisors (155927520).

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

51639840 is a wasteful number, since it uses less digits than its factorization.

51639840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 173 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 51639840 is about 7186.0865566732. The cubic root of 51639840 is about 372.3873869456.

The spelling of 51639840 in words is "fifty-one million, six hundred thirty-nine thousand, eight hundred forty".