20121799681 has 4 divisors (see below), whose sum is σ = 20122241364. Its totient is φ = 20121358000.

The previous prime is 20121799679. The next prime is 20121799699. The reversal of 20121799681 is 18699712102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18699712102 = 2 ⋅9349856051.

It can be written as a sum of positive squares in 2 ways, for example, as 5389909056 + 14731890625 = 73416^2 + 121375^2 .

It is a cyclic number.

It is not a de Polignac number, because 20121799681 - 2¹ = 20121799679 is a prime.

It is a super-2 number, since 2×20121799681² (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 (20121799631) 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, 143470 + ... + 246631.

It is an arithmetic number, because the mean of its divisors is an integer number (5030560341).

Almost surely, 2^20121799681 is an apocalyptic number.

It is an amenable number.

20121799681 is a deficient number, since it is larger than the sum of its proper divisors (441683).

20121799681 is an equidigital number, since it uses as much as digits as its factorization.

20121799681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441682.

The product of its (nonzero) digits is 108864, while the sum is 46.

The spelling of 20121799681 in words is "twenty billion, one hundred twenty-one million, seven hundred ninety-nine thousand, six hundred eighty-one".