631721 has 4 divisors (see below), whose sum is σ = 633600. Its totient is φ = 629844.

The previous prime is 631717. The next prime is 631723. The reversal of 631721 is 127136.

It is a happy number.

631721 is nontrivially palindromic in base 16.

631721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 631721 - 2² = 631717 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 631693 and 631702.

It is not an unprimeable number, because it can be changed into a prime (631723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 281 + ... + 1158.

It is an arithmetic number, because the mean of its divisors is an integer number (158400).

2⁶³¹⁷²¹ is an apocalyptic number.

It is an amenable number.

631721 is a deficient number, since it is larger than the sum of its proper divisors (1879).

631721 is a wasteful number, since it uses less digits than its factorization.

631721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1878.

The product of its digits is 252, while the sum is 20.

The square root of 631721 is about 794.8087820350. The cubic root of 631721 is about 85.8041785755.

Adding to 631721 its reverse (127136), we get a palindrome (758857).

The spelling of 631721 in words is "six hundred thirty-one thousand, seven hundred twenty-one".