643646 has 4 divisors (see below), whose sum is σ = 965472. Its totient is φ = 321822.

The previous prime is 643639. The next prime is 643649. The reversal of 643646 is 646346.

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

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643646.

It is not an unprimeable number, because it can be changed into a prime (643649) by changing a digit.

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 as a sum of consecutive naturals, namely, 160910 + ... + 160913.

It is an arithmetic number, because the mean of its divisors is an integer number (241368).

2⁶⁴³⁶⁴⁶ is an apocalyptic number.

643646 is a deficient number, since it is larger than the sum of its proper divisors (321826).

643646 is a wasteful number, since it uses less digits than its factorization.

643646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321825.

The product of its digits is 10368, while the sum is 29.

The square root of 643646 is about 802.2755137732. The cubic root of 643646 is about 86.3407250901.

The spelling of 643646 in words is "six hundred forty-three thousand, six hundred forty-six".