20997909697536 has 220 divisors, whose sum is σ = 62715635381652. Its totient is φ = 6997989261312.

The previous prime is 20997909697529. The next prime is 20997909697603. The reversal of 20997909697536 is 63579690979902.

20997909697536 is a `hidden beast` number, since 2 + 0 + 9 + 9 + 79 + 0 + 9 + 6 + 9 + 7 + 536 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 14316718657536 + 6681191040000 = 3783744^2 + 2584800^2 .

It is a Harshad number since it is a multiple of its sum of digits (81).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 507015966 + ... + 507057378.

Almost surely, 2^{20997909697536} 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 20997909697536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31357817690826).

20997909697536 is an abundant number, since it is smaller than the sum of its proper divisors (41717725684116).

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

20997909697536 is an equidigital number, since it uses as much as digits as its factorization.

20997909697536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47558 (or 47531 counting only the distinct ones).

The product of its (nonzero) digits is 3124873080, while the sum is 81.

The spelling of 20997909697536 in words is "twenty trillion, nine hundred ninety-seven billion, nine hundred nine million, six hundred ninety-seven thousand, five hundred thirty-six".