20718365881 has 4 divisors (see below), whose sum is σ = 20718871632. Its totient is φ = 20717860132.

The previous prime is 20718365827. The next prime is 20718365893. The reversal of 20718365881 is 18856381702.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18856381702 = 2 ⋅9428190851.

It is a cyclic number.

It is not a de Polignac number, because 20718365881 - 2¹¹ = 20718363833 is a prime.

It is a super-2 number, since 2×20718365881² (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 (20718365581) 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, 185431 + ... + 275356.

It is an arithmetic number, because the mean of its divisors is an integer number (5179717908).

Almost surely, 2^20718365881 is an apocalyptic number.

It is an amenable number.

20718365881 is a deficient number, since it is larger than the sum of its proper divisors (505751).

20718365881 is an equidigital number, since it uses as much as digits as its factorization.

20718365881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 505750.

The product of its (nonzero) digits is 645120, while the sum is 49.

The spelling of 20718365881 in words is "twenty billion, seven hundred eighteen million, three hundred sixty-five thousand, eight hundred eighty-one".