20985788993 has 4 divisors (see below), whose sum is σ = 22600080468. Its totient is φ = 19371497520.

The previous prime is 20985788939. The next prime is 20985789023. The reversal of 20985788993 is 39988758902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 39988758902 = 2 ⋅19994379451.

It can be written as a sum of positive squares in 2 ways, for example, as 7178833984 + 13806955009 = 84728^2 + 117503^2 .

It is a cyclic number.

It is not a de Polignac number, because 20985788993 - 2¹⁴ = 20985772609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20985788393) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 807145718 + ... + 807145743.

It is an arithmetic number, because the mean of its divisors is an integer number (5650020117).

Almost surely, 2^20985788993 is an apocalyptic number.

It is an amenable number.

20985788993 is a deficient number, since it is larger than the sum of its proper divisors (1614291475).

20985788993 is a wasteful number, since it uses less digits than its factorization.

20985788993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1614291474.

The product of its (nonzero) digits is 78382080, while the sum is 68.

The spelling of 20985788993 in words is "twenty billion, nine hundred eighty-five million, seven hundred eighty-eight thousand, nine hundred ninety-three".