20005665643 has 4 divisors (see below), whose sum is σ = 20651009728. Its totient is φ = 19360321560.

The previous prime is 20005665601. The next prime is 20005665683. The reversal of 20005665643 is 34656650002.

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

It is a cyclic number.

It is not a de Polignac number, because 20005665643 - 2²¹ = 20003568491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20005665683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 322671996 + ... + 322672057.

It is an arithmetic number, because the mean of its divisors is an integer number (5162752432).

Almost surely, 2^20005665643 is an apocalyptic number.

20005665643 is a deficient number, since it is larger than the sum of its proper divisors (645344085).

20005665643 is an equidigital number, since it uses as much as digits as its factorization.

20005665643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 645344084.

The product of its (nonzero) digits is 129600, while the sum is 37.

The spelling of 20005665643 in words is "twenty billion, five million, six hundred sixty-five thousand, six hundred forty-three".