20871812681 has 4 divisors (see below), whose sum is σ = 20872693200. Its totient is φ = 20870932164.

The previous prime is 20871812659. The next prime is 20871812693. The reversal of 20871812681 is 18621817802.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20871812681 - 2⁶ = 20871812617 is a prime.

It is a super-2 number, since 2×20871812681² (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 (20871812281) 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, 403691 + ... + 452448.

It is an arithmetic number, because the mean of its divisors is an integer number (5218173300).

Almost surely, 2^20871812681 is an apocalyptic number.

It is an amenable number.

20871812681 is a deficient number, since it is larger than the sum of its proper divisors (880519).

20871812681 is an equidigital number, since it uses as much as digits as its factorization.

20871812681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 880518.

The product of its (nonzero) digits is 86016, while the sum is 44.

The spelling of 20871812681 in words is "twenty billion, eight hundred seventy-one million, eight hundred twelve thousand, six hundred eighty-one".