21876658721 has 2 divisors, whose sum is σ = 21876658722. Its totient is φ = 21876658720.

The previous prime is 21876658697. The next prime is 21876658757. The reversal of 21876658721 is 12785667812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16753678096 + 5122980625 = 129436^2 + 71575^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21876658721 is a prime.

It is not a weakly prime, because it can be changed into another prime (21876658781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10938329360 + 10938329361.

It is an arithmetic number, because the mean of its divisors is an integer number (10938329361).

Almost surely, 2^21876658721 is an apocalyptic number.

It is an amenable number.

21876658721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21876658721 is an equidigital number, since it uses as much as digits as its factorization.

21876658721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2257920, while the sum is 53.

Subtracting from 21876658721 its reverse (12785667812), we obtain a palindrome (9090990909).

The spelling of 21876658721 in words is "twenty-one billion, eight hundred seventy-six million, six hundred fifty-eight thousand, seven hundred twenty-one".