21518316998656 has 39 divisors (see below), whose sum is σ = 43031974202013. Its totient is φ = 10759010058240.

The previous prime is 21518316998653. The next prime is 21518316998687. The reversal of 21518316998656 is 65689961381512.

It is a happy number.

The square root of 21518316998656 is 4638784.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 7815289901056 + 13703027097600 = 2795584^2 + 3701760^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21518316998653) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 296845936 + ... + 296918416.

Almost surely, 2^{21518316998656} is an apocalyptic number.

21518316998656 is the 4638784-th square number.

It is an amenable number.

21518316998656 is a deficient number, since it is larger than the sum of its proper divisors (21513657203357).

21518316998656 is an frugal number, since it uses more digits than its factorization.

21518316998656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144986 (or 72483 counting only the distinct ones).

The product of its digits is 167961600, while the sum is 70.

The spelling of 21518316998656 in words is "twenty-one trillion, five hundred eighteen billion, three hundred sixteen million, nine hundred ninety-eight thousand, six hundred fifty-six".