20006643 has 4 divisors (see below), whose sum is σ = 26675528. Its totient is φ = 13337760.

The previous prime is 20006641. The next prime is 20006663. The reversal of 20006643 is 34660002.

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

It is not a de Polignac number, because 20006643 - 2¹ = 20006641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20006641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3334438 + ... + 3334443.

It is an arithmetic number, because the mean of its divisors is an integer number (6668882).

Almost surely, 2^20006643 is an apocalyptic number.

20006643 is a deficient number, since it is larger than the sum of its proper divisors (6668885).

20006643 is an equidigital number, since it uses as much as digits as its factorization.

20006643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6668884.

The product of its (nonzero) digits is 864, while the sum is 21.

The square root of 20006643 is about 4472.8786033158. The cubic root of 20006643 is about 271.4718114598.

Adding to 20006643 its reverse (34660002), we get a palindrome (54666645).

The spelling of 20006643 in words is "twenty million, six thousand, six hundred forty-three".