20685447985 has 8 divisors (see below), whose sum is σ = 24857951976. Its totient is φ = 16524748800.

The previous prime is 20685447971. The next prime is 20685447997. The reversal of 20685447985 is 58974458602.

It can be written as a sum of positive squares in 4 ways, for example, as 11692529424 + 8992918561 = 108132^2 + 94831^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20685447985 - 2¹⁷ = 20685316913 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2947344 + ... + 2954353.

It is an arithmetic number, because the mean of its divisors is an integer number (3107243997).

Almost surely, 2^20685447985 is an apocalyptic number.

It is an amenable number.

20685447985 is a deficient number, since it is larger than the sum of its proper divisors (4172503991).

20685447985 is an equidigital number, since it uses as much as digits as its factorization.

20685447985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5902403.

The product of its (nonzero) digits is 19353600, while the sum is 58.

The spelling of 20685447985 in words is "twenty billion, six hundred eighty-five million, four hundred forty-seven thousand, nine hundred eighty-five".