643636 has 24 divisors (see below), whose sum is σ = 1304576. Its totient is φ = 272160.

The previous prime is 643633. The next prime is 643639. The reversal of 643636 is 636346.

643636 is nontrivially palindromic in base 9.

It is an interprime number because it is at equal distance from previous prime (643633) and next prime (643639).

It is a Harshad number since it is a multiple of its sum of digits (28).

643636 is a modest number, since divided by 3636 gives 64 as remainder.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3466 + ... + 3646.

2⁶⁴³⁶³⁶ is an apocalyptic number.

It is an amenable number.

643636 is an abundant number, since it is smaller than the sum of its proper divisors (660940).

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

643636 is a wasteful number, since it uses less digits than its factorization.

643636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319 (or 317 counting only the distinct ones).

The product of its digits is 7776, while the sum is 28.

The square root of 643636 is about 802.2692814760. The cubic root of 643636 is about 86.3402779438.

The spelling of 643636 in words is "six hundred forty-three thousand, six hundred thirty-six".