637668 has 18 divisors (see below), whose sum is σ = 1611974. Its totient is φ = 212544.

The previous prime is 637657. The next prime is 637669. The reversal of 637668 is 866736.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 627264 + 10404 = 792^2 + 102^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 17713 = 637668 / (6 + 3 + 7 + 6 + 6 + 8).

It is not an unprimeable number, because it can be changed into a prime (637669) by changing a digit.

637668 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 5 ways as a sum of consecutive naturals, for example, 8821 + ... + 8892.

2⁶³⁷⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

637668 is an abundant number, since it is smaller than the sum of its proper divisors (974306).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

637668 is a wasteful number, since it uses less digits than its factorization.

637668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17723 (or 17718 counting only the distinct ones).

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

The square root of 637668 is about 798.5411698842. The cubic root of 637668 is about 86.0725905946.

The spelling of 637668 in words is "six hundred thirty-seven thousand, six hundred sixty-eight".