21010020091 has 2 divisors, whose sum is σ = 21010020092. Its totient is φ = 21010020090.

The previous prime is 21010020071. The next prime is 21010020113. The reversal of 21010020091 is 19002001012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21010020091 - 2¹³ = 21010011899 is a prime.

It is not a weakly prime, because it can be changed into another prime (21010020071) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505010045 + 10505010046.

It is an arithmetic number, because the mean of its divisors is an integer number (10505010046).

Almost surely, 2^21010020091 is an apocalyptic number.

21010020091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010020091 is an equidigital number, since it uses as much as digits as its factorization.

21010020091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 16.

The spelling of 21010020091 in words is "twenty-one billion, ten million, twenty thousand, ninety-one".