21643544563 has 8 divisors (see below), whose sum is σ = 21713291600. Its totient is φ = 21573842400.

The previous prime is 21643544557. The next prime is 21643544569. The reversal of 21643544563 is 36544534612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21643544557) and next prime (21643544569).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21643544563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21643544569) 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 7 ways as a sum of consecutive naturals, for example, 1142656 + ... + 1161442.

It is an arithmetic number, because the mean of its divisors is an integer number (2714161450).

Almost surely, 2^21643544563 is an apocalyptic number.

21643544563 is a deficient number, since it is larger than the sum of its proper divisors (69747037).

21643544563 is a wasteful number, since it uses less digits than its factorization.

21643544563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22437.

The product of its digits is 1036800, while the sum is 43.

The spelling of 21643544563 in words is "twenty-one billion, six hundred forty-three million, five hundred forty-four thousand, five hundred sixty-three".