26991167921 has 2 divisors, whose sum is σ = 26991167922. Its totient is φ = 26991167920.

The previous prime is 26991167857. The next prime is 26991167939. The reversal of 26991167921 is 12976119962.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20516551696 + 6474616225 = 143236^2 + 80465^2 .

It is a cyclic number.

It is not a de Polignac number, because 26991167921 - 2⁶ = 26991167857 is a prime.

It is not a weakly prime, because it can be changed into another prime (26991167521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13495583960 + 13495583961.

It is an arithmetic number, because the mean of its divisors is an integer number (13495583961).

Almost surely, 2^26991167921 is an apocalyptic number.

It is an amenable number.

26991167921 is a deficient number, since it is larger than the sum of its proper divisors (1).

26991167921 is an equidigital number, since it uses as much as digits as its factorization.

26991167921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 734832, while the sum is 53.

The spelling of 26991167921 in words is "twenty-six billion, nine hundred ninety-one million, one hundred sixty-seven thousand, nine hundred twenty-one".