636840 has 96 divisors (see below), whose sum is σ = 2176200. Its totient is φ = 161280.

The previous prime is 636829. The next prime is 636851. The reversal of 636840 is 48636.

It is an interprime number because it is at equal distance from previous prime (636829) and next prime (636851).

It can be written as a sum of positive squares in 4 ways, for example, as 338724 + 298116 = 582^2 + 546^2 .

It is an unprimeable 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 23 ways as a sum of consecutive naturals, for example, 10410 + ... + 10470.

2⁶³⁶⁸⁴⁰ is an apocalyptic number.

636840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 636840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1088100).

636840 is an abundant number, since it is smaller than the sum of its proper divisors (1539360).

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

636840 is a wasteful number, since it uses less digits than its factorization.

636840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107 (or 100 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 636840 is about 798.0225560722. The cubic root of 636840 is about 86.0353199072.

It can be divided in two parts, 63 and 6840, that added together give a triangular number (6903 = T₁₁₇).

The spelling of 636840 in words is "six hundred thirty-six thousand, eight hundred forty".