51721856 has 64 divisors (see below), whose sum is σ = 108062880. Its totient is φ = 24634368.

The previous prime is 51721847. The next prime is 51721861. The reversal of 51721856 is 65812715.

It is a tau number, because it is divible by the number of its divisors (64).

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 317231 + ... + 317393.

Almost surely, 2^51721856 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 51721856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (54031440).

51721856 is an abundant number, since it is smaller than the sum of its proper divisors (56341024).

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

51721856 is a wasteful number, since it uses less digits than its factorization.

51721856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281 (or 269 counting only the distinct ones).

The product of its digits is 16800, while the sum is 35.

The square root of 51721856 is about 7191.7908757138. The cubic root of 51721856 is about 372.5844284100.

The spelling of 51721856 in words is "fifty-one million, seven hundred twenty-one thousand, eight hundred fifty-six".