20681891345 has 8 divisors (see below), whose sum is σ = 25286539176. Its totient is φ = 16233333376.

The previous prime is 20681891317. The next prime is 20681891357. The reversal of 20681891345 is 54319818602.

It is a happy number.

It is a Cunningham number, because it is equal to 143812²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 7445618944 + 13236272401 = 86288^2 + 115049^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20681891345 - 2²⁶ = 20614782481 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20681891345.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39022172 + ... + 39022701.

It is an arithmetic number, because the mean of its divisors is an integer number (3160817397).

Almost surely, 2^20681891345 is an apocalyptic number.

It is an amenable number.

20681891345 is a deficient number, since it is larger than the sum of its proper divisors (4604647831).

20681891345 is an equidigital number, since it uses as much as digits as its factorization.

20681891345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78044931.

The product of its (nonzero) digits is 414720, while the sum is 47.

The spelling of 20681891345 in words is "twenty billion, six hundred eighty-one million, eight hundred ninety-one thousand, three hundred forty-five".