631664721 has 12 divisors (see below), whose sum is σ = 915877248. Its totient is φ = 419507064.

The previous prime is 631664681. The next prime is 631664723. The reversal of 631664721 is 127466136.

It is a happy number.

631664721 is a `hidden beast` number, since 6 + 3 + 1 + 6 + 647 + 2 + 1 = 666.

It is not a de Polignac number, because 631664721 - 2²³ = 623276113 is a prime.

It is not an unprimeable number, because it can be changed into a prime (631664723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 131065 + ... + 135798.

It is an arithmetic number, because the mean of its divisors is an integer number (76323104).

Almost surely, 2^631664721 is an apocalyptic number.

It is an amenable number.

631664721 is a deficient number, since it is larger than the sum of its proper divisors (284212527).

631664721 is a wasteful number, since it uses less digits than its factorization.

631664721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267132 (or 267129 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 631664721 is about 25132.9409540547. The cubic root of 631664721 is about 858.0163044809.

The spelling of 631664721 in words is "six hundred thirty-one million, six hundred sixty-four thousand, seven hundred twenty-one".