21643020561 has 8 divisors (see below), whose sum is σ = 28917607680. Its totient is φ = 14398556912.

The previous prime is 21643020557. The next prime is 21643020571. The reversal of 21643020561 is 16502034612.

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

It is a cyclic number.

It is not a de Polignac number, because 21643020561 - 2² = 21643020557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21643020541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7529190 + ... + 7532063.

It is an arithmetic number, because the mean of its divisors is an integer number (3614700960).

Almost surely, 2^21643020561 is an apocalyptic number.

It is an amenable number.

21643020561 is a deficient number, since it is larger than the sum of its proper divisors (7274587119).

21643020561 is a wasteful number, since it uses less digits than its factorization.

21643020561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15061735.

The product of its (nonzero) digits is 8640, while the sum is 30.

The spelling of 21643020561 in words is "twenty-one billion, six hundred forty-three million, twenty thousand, five hundred sixty-one".