643434621 has 4 divisors (see below), whose sum is σ = 857912832. Its totient is φ = 428956412.

The previous prime is 643434619. The next prime is 643434661. The reversal of 643434621 is 126434346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 643434621 - 2¹ = 643434619 is a prime.

It is a super-2 number, since 2×643434621² = 828016223002827282, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643434661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107239101 + ... + 107239106.

It is an arithmetic number, because the mean of its divisors is an integer number (214478208).

Almost surely, 2^643434621 is an apocalyptic number.

It is an amenable number.

643434621 is a deficient number, since it is larger than the sum of its proper divisors (214478211).

643434621 is a wasteful number, since it uses less digits than its factorization.

643434621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214478210.

The product of its digits is 41472, while the sum is 33.

The square root of 643434621 is about 25366.0131080941. The cubic root of 643434621 is about 863.3127237104.

Adding to 643434621 its reverse (126434346), we get a palindrome (769868967).

The spelling of 643434621 in words is "six hundred forty-three million, four hundred thirty-four thousand, six hundred twenty-one".