637 has 6 divisors (see below), whose sum is σ = 798. Its totient is φ = 504.

The previous prime is 631. The next prime is 641. The reversal of 637 is 736.

It is a happy number.

637 is nontrivially palindromic in base 9.

637 is an esthetic number in base 3, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in only one way, i.e., 441 + 196 = 21^2 + 14^2 .

It is not a de Polignac number, because 637 - 2⁷ = 509 is a prime.

637 is an undulating number in base 3.

637 is a nontrivial repdigit in base 9.

It is a plaindrome in base 9, base 14 and base 16.

It is a nialpdrome in base 9.

It is a zygodrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 637.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 43 + ... + 55.

It is an arithmetic number, because the mean of its divisors is an integer number (133).

637 is the 13-th decagonal number.

It is an amenable number.

637 is a deficient number, since it is larger than the sum of its proper divisors (161).

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

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

The sum of its prime factors is 27 (or 20 counting only the distinct ones).

The product of its digits is 126, while the sum is 16.

The square root of 637 is about 25.2388589282. The cubic root of 637 is about 8.6042524490.

Subtracting 637 from its reverse (736), we obtain a palindrome (99).

It can be divided in two parts, 63 and 7, that multiplied together give a square (441 = 21²).

The spelling of 637 in words is "six hundred thirty-seven", and thus it is an aban number and an oban number.