21025000091 has 2 divisors, whose sum is σ = 21025000092. Its totient is φ = 21025000090.

The previous prime is 21025000063. The next prime is 21025000109. The reversal of 21025000091 is 19000052012.

Together with next prime (21025000109) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21025000091 - 2²² = 21020805787 is a prime.

It is not a weakly prime, because it can be changed into another prime (21025000021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10512500045 + 10512500046.

It is an arithmetic number, because the mean of its divisors is an integer number (10512500046).

Almost surely, 2^21025000091 is an apocalyptic number.

21025000091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21025000091 is an equidigital number, since it uses as much as digits as its factorization.

21025000091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 20.

The spelling of 21025000091 in words is "twenty-one billion, twenty-five million, ninety-one", and thus it is an aban number and an uban number.