21261304091 has 2 divisors, whose sum is σ = 21261304092. Its totient is φ = 21261304090.

The previous prime is 21261304087. The next prime is 21261304147. The reversal of 21261304091 is 19040316212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21261304091 - 2² = 21261304087 is a prime.

It is not a weakly prime, because it can be changed into another prime (21261304991) 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, 10630652045 + 10630652046.

It is an arithmetic number, because the mean of its divisors is an integer number (10630652046).

Almost surely, 2^21261304091 is an apocalyptic number.

21261304091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21261304091 is an equidigital number, since it uses as much as digits as its factorization.

21261304091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 29.

The spelling of 21261304091 in words is "twenty-one billion, two hundred sixty-one million, three hundred four thousand, ninety-one".