21005543563 has 2 divisors, whose sum is σ = 21005543564. Its totient is φ = 21005543562.

The previous prime is 21005543561. The next prime is 21005543593. The reversal of 21005543563 is 36534550012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21005543563 - 2¹ = 21005543561 is a prime.

Together with 21005543561, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21005543561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502771781 + 10502771782.

It is an arithmetic number, because the mean of its divisors is an integer number (10502771782).

Almost surely, 2^21005543563 is an apocalyptic number.

21005543563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005543563 is an equidigital number, since it uses as much as digits as its factorization.

21005543563 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 54000, while the sum is 34.

The spelling of 21005543563 in words is "twenty-one billion, five million, five hundred forty-three thousand, five hundred sixty-three".