21001021099 has 4 divisors (see below), whose sum is σ = 21042773136. Its totient is φ = 20959269064.

The previous prime is 21001021091. The next prime is 21001021103. The reversal of 21001021099 is 99012010012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21001021099 - 2³ = 21001021091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001021091) 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 in 3 ways as a sum of consecutive naturals, for example, 20875264 + ... + 20876269.

It is an arithmetic number, because the mean of its divisors is an integer number (5260693284).

Almost surely, 2^21001021099 is an apocalyptic number.

21001021099 is a deficient number, since it is larger than the sum of its proper divisors (41752037).

21001021099 is an equidigital number, since it uses as much as digits as its factorization.

21001021099 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41752036.

The product of its (nonzero) digits is 324, while the sum is 25.

The spelling of 21001021099 in words is "twenty-one billion, one million, twenty-one thousand, ninety-nine".