643562021 has 4 divisors (see below), whose sum is σ = 648259692. Its totient is φ = 638864352.

The previous prime is 643561991. The next prime is 643562033. The reversal of 643562021 is 120265346.

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

It can be written as a sum of positive squares in 2 ways, for example, as 119793025 + 523768996 = 10945^2 + 22886^2 .

It is a cyclic number.

It is not a de Polignac number, because 643562021 - 2⁶ = 643561957 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 (643561021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2348630 + ... + 2348903.

It is an arithmetic number, because the mean of its divisors is an integer number (162064923).

Almost surely, 2^643562021 is an apocalyptic number.

It is an amenable number.

643562021 is a deficient number, since it is larger than the sum of its proper divisors (4697671).

643562021 is a wasteful number, since it uses less digits than its factorization.

643562021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4697670.

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 643562021 is about 25368.5242180147. The cubic root of 643562021 is about 863.3696985654.

The spelling of 643562021 in words is "six hundred forty-three million, five hundred sixty-two thousand, twenty-one".