51668640 has 144 divisors (see below), whose sum is σ = 179911368. Its totient is φ = 13498368.

The previous prime is 51668621. The next prime is 51668677. The reversal of 51668640 is 4686615.

51668640 is a `hidden beast` number, since 5 + 1 + 6 + 6 + 8 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 51667344 + 1296 = 7188^2 + 36^2 .

It is a tau number, because it is divible by the number of its divisors (144).

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 = 51668595 and 51668604.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 75982 + ... + 76658.

Almost surely, 2^51668640 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 51668640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89955684).

51668640 is an abundant number, since it is smaller than the sum of its proper divisors (128242728).

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

51668640 is a wasteful number, since it uses less digits than its factorization.

51668640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 751 (or 740 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The square root of 51668640 is about 7188.0901496851. The cubic root of 51668640 is about 372.4566020039.

The spelling of 51668640 in words is "fifty-one million, six hundred sixty-eight thousand, six hundred forty".