631661 has 4 divisors (see below), whose sum is σ = 634524. Its totient is φ = 628800.

The previous prime is 631643. The next prime is 631667. The reversal of 631661 is 166136.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 498436 + 133225 = 706^2 + 365^2 .

It is a cyclic number.

It is not a de Polignac number, because 631661 - 2⁶ = 631597 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 631661.

It is not an unprimeable number, because it can be changed into a prime (631667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1070 + ... + 1551.

It is an arithmetic number, because the mean of its divisors is an integer number (158631).

2⁶³¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

631661 is a deficient number, since it is larger than the sum of its proper divisors (2863).

631661 is a wasteful number, since it uses less digits than its factorization.

631661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2862.

The product of its digits is 648, while the sum is 23.

The square root of 631661 is about 794.7710362111. The cubic root of 631661 is about 85.8014619682.

Adding to 631661 its reverse (166136), we get a palindrome (797797).

The spelling of 631661 in words is "six hundred thirty-one thousand, six hundred sixty-one".