20990998656 has 192 divisors, whose sum is σ = 62688214680. Its totient is φ = 6736379904.

The previous prime is 20990998627. The next prime is 20990998673. The reversal of 20990998656 is 65689909902.

It can be written as a sum of positive squares in 4 ways, for example, as 20701454400 + 289544256 = 143880^2 + 17016^2 .

It is a tau number, because it is divible by the number of its divisors (192).

It is a junction number, because it is equal to n+sod(n) for n = 20990998593 and 20990998602.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4131990 + ... + 4137066.

Almost surely, 2^20990998656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20990998656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31344107340).

20990998656 is an abundant number, since it is smaller than the sum of its proper divisors (41697216024).

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

20990998656 is a wasteful number, since it uses less digits than its factorization.

20990998656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5231 (or 5216 counting only the distinct ones).

The product of its (nonzero) digits is 18895680, while the sum is 63.

The spelling of 20990998656 in words is "twenty billion, nine hundred ninety million, nine hundred ninety-eight thousand, six hundred fifty-six".