21000001091 has 2 divisors, whose sum is σ = 21000001092. Its totient is φ = 21000001090.

The previous prime is 21000001069. The next prime is 21000001153. The reversal of 21000001091 is 19010000012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21000001091 - 2²² = 20995806787 is a prime.

It is not a weakly prime, because it can be changed into another prime (21000006091) 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, 10500000545 + 10500000546.

It is an arithmetic number, because the mean of its divisors is an integer number (10500000546).

Almost surely, 2^21000001091 is an apocalyptic number.

21000001091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000001091 is an equidigital number, since it uses as much as digits as its factorization.

21000001091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18, while the sum is 14.

The spelling of 21000001091 in words is "twenty-one billion, one thousand, ninety-one".