20871851431 has 4 divisors (see below), whose sum is σ = 20872406152. Its totient is φ = 20871296712.

The previous prime is 20871851417. The next prime is 20871851447. The reversal of 20871851431 is 13415817802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13415817802 = 2 ⋅6707908901.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20871851431 is a prime.

It is a super-2 number, since 2×20871851431² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20871851411) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 216465 + ... + 297658.

It is an arithmetic number, because the mean of its divisors is an integer number (5218101538).

Almost surely, 2^20871851431 is an apocalyptic number.

20871851431 is a deficient number, since it is larger than the sum of its proper divisors (554721).

20871851431 is an equidigital number, since it uses as much as digits as its factorization.

20871851431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 554720.

The product of its (nonzero) digits is 53760, while the sum is 40.

The spelling of 20871851431 in words is "twenty billion, eight hundred seventy-one million, eight hundred fifty-one thousand, four hundred thirty-one".