636891 has 4 divisors (see below), whose sum is σ = 849192. Its totient is φ = 424592.

The previous prime is 636877. The next prime is 636917. The reversal of 636891 is 198636.

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

It is a cyclic number.

It is not a de Polignac number, because 636891 - 2⁷ = 636763 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (636821) 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, 106146 + ... + 106151.

It is an arithmetic number, because the mean of its divisors is an integer number (212298).

2⁶³⁶⁸⁹¹ is an apocalyptic number.

636891 is a deficient number, since it is larger than the sum of its proper divisors (212301).

636891 is a wasteful number, since it uses less digits than its factorization.

636891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212300.

The product of its digits is 7776, while the sum is 33.

The square root of 636891 is about 798.0545094165. The cubic root of 636891 is about 86.0376164989.

The spelling of 636891 in words is "six hundred thirty-six thousand, eight hundred ninety-one".