It is a happy number.
5721721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.
It is a sphenic number, since it is the product of 3 distinct primes.
It is a cyclic number.
It is an Ulam number.
It is a Duffinian number.
It is a congruent number.
Almost surely, 25721721 is an apocalyptic number.
It is an amenable number.
5721721 is a wasteful number, since it uses less digits than its factorization.
5721721 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 1355.
The square root of 5721721 is about 2392.0119146860. The cubic root of 5721721 is about 178.8582150740.
Adding to 5721721 its reverse (1271275), we get a palindrome (6992996).
The spelling of 5721721 in words is "five million, seven hundred twenty-one thousand, seven hundred twenty-one".