643629821 has 8 divisors (see below), whose sum is σ = 648735360. Its totient is φ = 638537328.

The previous prime is 643629817. The next prime is 643629841. The reversal of 643629821 is 128926346.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 643629821 - 2² = 643629817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643629841) 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, 111320 + ... + 116958.

It is an arithmetic number, because the mean of its divisors is an integer number (81091920).

Almost surely, 2^643629821 is an apocalyptic number.

It is an amenable number.

643629821 is a deficient number, since it is larger than the sum of its proper divisors (5105539).

643629821 is a wasteful number, since it uses less digits than its factorization.

643629821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6523.

The product of its digits is 124416, while the sum is 41.

The square root of 643629821 is about 25369.8604844410. The cubic root of 643629821 is about 863.4000164981.

The spelling of 643629821 in words is "six hundred forty-three million, six hundred twenty-nine thousand, eight hundred twenty-one".