631128661 has 4 divisors (see below), whose sum is σ = 631539232. Its totient is φ = 630718092.

The previous prime is 631128629. The next prime is 631128679. The reversal of 631128661 is 166821136.

It is a happy number.

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 631128661 - 2⁵ = 631128629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (631128601) 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, 202971 + ... + 206056.

It is an arithmetic number, because the mean of its divisors is an integer number (157884808).

Almost surely, 2^631128661 is an apocalyptic number.

It is an amenable number.

631128661 is a deficient number, since it is larger than the sum of its proper divisors (410571).

631128661 is a wasteful number, since it uses less digits than its factorization.

631128661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410570.

The product of its digits is 10368, while the sum is 34.

The square root of 631128661 is about 25122.2742003983. The cubic root of 631128661 is about 857.7735183016.

Adding to 631128661 its reverse (166821136), we get a palindrome (797949797).

The spelling of 631128661 in words is "six hundred thirty-one million, one hundred twenty-eight thousand, six hundred sixty-one".