20871800647 has 4 divisors (see below), whose sum is σ = 21225560040. Its totient is φ = 20518041256.

The previous prime is 20871800641. The next prime is 20871800657. The reversal of 20871800647 is 74600817802.

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

It is a cyclic number.

It is not a de Polignac number, because 20871800647 - 2²³ = 20863412039 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20871800641) 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, 176879608 + ... + 176879725.

It is an arithmetic number, because the mean of its divisors is an integer number (5306390010).

Almost surely, 2^20871800647 is an apocalyptic number.

20871800647 is a deficient number, since it is larger than the sum of its proper divisors (353759393).

20871800647 is an equidigital number, since it uses as much as digits as its factorization.

20871800647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 353759392.

The product of its (nonzero) digits is 150528, while the sum is 43.

The spelling of 20871800647 in words is "twenty billion, eight hundred seventy-one million, eight hundred thousand, six hundred forty-seven".