20447856017 has 4 divisors (see below), whose sum is σ = 20585090100. Its totient is φ = 20310621936.

The previous prime is 20447855977. The next prime is 20447856019. The reversal of 20447856017 is 71065874402.

It is a Cunningham number, because it is equal to 142996²+1.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2395515136 + 18052340881 = 48944^2 + 134359^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20447856017 is a prime.

It is a super-2 number, since 2×20447856017² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20447856019) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68616818 + ... + 68617115.

It is an arithmetic number, because the mean of its divisors is an integer number (5146272525).

Almost surely, 2^20447856017 is an apocalyptic number.

It is an amenable number.

20447856017 is a deficient number, since it is larger than the sum of its proper divisors (137234083).

20447856017 is a wasteful number, since it uses less digits than its factorization.

20447856017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137234082.

The product of its (nonzero) digits is 376320, while the sum is 44.

The spelling of 20447856017 in words is "twenty billion, four hundred forty-seven million, eight hundred fifty-six thousand, seventeen".