21001021091 has 2 divisors, whose sum is σ = 21001021092. Its totient is φ = 21001021090.

The previous prime is 21001021073. The next prime is 21001021103. The reversal of 21001021091 is 19012010012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21001021091 - 2²² = 20996826787 is a prime.

It is not a weakly prime, because it can be changed into another prime (21001021061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500510545 + 10500510546.

It is an arithmetic number, because the mean of its divisors is an integer number (10500510546).

Almost surely, 2^21001021091 is an apocalyptic number.

21001021091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001021091 is an equidigital number, since it uses as much as digits as its factorization.

21001021091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36, while the sum is 17.

The spelling of 21001021091 in words is "twenty-one billion, one million, twenty-one thousand, ninety-one".