643623221 has 4 divisors (see below), whose sum is σ = 645897792. Its totient is φ = 641348652.

The previous prime is 643623193. The next prime is 643623229. The reversal of 643623221 is 122326346.

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 643623221 - 2¹⁴ = 643606837 is a prime.

It is a super-2 number, since 2×643623221² = 828501701220829682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643623229) 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, 1136861 + ... + 1137426.

It is an arithmetic number, because the mean of its divisors is an integer number (161474448).

Almost surely, 2^643623221 is an apocalyptic number.

It is an amenable number.

643623221 is a deficient number, since it is larger than the sum of its proper divisors (2274571).

643623221 is a wasteful number, since it uses less digits than its factorization.

643623221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2274570.

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

The square root of 643623221 is about 25369.7304085006. The cubic root of 643623221 is about 863.3970652885.

Adding to 643623221 its reverse (122326346), we get a palindrome (765949567).

The spelling of 643623221 in words is "six hundred forty-three million, six hundred twenty-three thousand, two hundred twenty-one".