643408 has 10 divisors (see below), whose sum is σ = 1246634. Its totient is φ = 321696.

The previous prime is 643403. The next prime is 643421. The reversal of 643408 is 804346.

It can be written as a sum of positive squares in only one way, i.e., 535824 + 107584 = 732^2 + 328^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643403) by changing a digit.

643408 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20091 + ... + 20122.

2⁶⁴³⁴⁰⁸ is an apocalyptic number.

It is an amenable number.

643408 is a deficient number, since it is larger than the sum of its proper divisors (603226).

643408 is a wasteful number, since it uses less digits than its factorization.

643408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40221 (or 40215 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 25.

The square root of 643408 is about 802.1271719622. The cubic root of 643408 is about 86.3300817520.

The spelling of 643408 in words is "six hundred forty-three thousand, four hundred eight".