21809553616 has 10 divisors (see below), whose sum is σ = 42256010162. Its totient is φ = 10904776800.

The previous prime is 21809553613. The next prime is 21809553629. The reversal of 21809553616 is 61635590812.

It can be written as a sum of positive squares in only one way, i.e., 18359166016 + 3450387600 = 135496^2 + 58740^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21809553611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 681548535 + ... + 681548566.

Almost surely, 2^21809553616 is an apocalyptic number.

It is an amenable number.

21809553616 is a deficient number, since it is larger than the sum of its proper divisors (20446456546).

21809553616 is a wasteful number, since it uses less digits than its factorization.

21809553616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1363097109 (or 1363097103 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 46.

The spelling of 21809553616 in words is "twenty-one billion, eight hundred nine million, five hundred fifty-three thousand, six hundred sixteen".