21643304656 has 20 divisors (see below), whose sum is σ = 44400603492. Its totient is φ = 10185084416.

The previous prime is 21643304651. The next prime is 21643304677. The reversal of 21643304656 is 65640334612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5821690000 + 15821614656 = 76300^2 + 125784^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21643304651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39785215 + ... + 39785758.

Almost surely, 2^21643304656 is an apocalyptic number.

It is an amenable number.

21643304656 is an abundant number, since it is smaller than the sum of its proper divisors (22757298836).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21643304656 is a wasteful number, since it uses less digits than its factorization.

21643304656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79570998 (or 79570992 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 40.

The spelling of 21643304656 in words is "twenty-one billion, six hundred forty-three million, three hundred four thousand, six hundred fifty-six".