51721720 has 32 divisors (see below), whose sum is σ = 116769600. Its totient is φ = 20618368.

The previous prime is 51721697. The next prime is 51721721. The reversal of 51721720 is 2712715.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51721721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10641 + ... + 14719.

It is an arithmetic number, because the mean of its divisors is an integer number (3649050).

Almost surely, 2^51721720 is an apocalyptic number.

It is an amenable number.

51721720 is an abundant number, since it is smaller than the sum of its proper divisors (65047880).

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

51721720 is a wasteful number, since it uses less digits than its factorization.

51721720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4407 (or 4403 counting only the distinct ones).

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 51721720 is about 7191.7814204827. The cubic root of 51721720 is about 372.5841018457.

It can be divided in two parts, 51721 and 720, that added together give a square (52441 = 229²).

The spelling of 51721720 in words is "fifty-one million, seven hundred twenty-one thousand, seven hundred twenty".