21012020020209 has 4 divisors (see below), whose sum is σ = 28016026693616. Its totient is φ = 14008013346804.

The previous prime is 21012020020141. The next prime is 21012020020331. The reversal of 21012020020209 is 90202002021012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21012020020209 - 2⁷ = 21012020020081 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21112020020209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3502003336699 + ... + 3502003336704.

It is an arithmetic number, because the mean of its divisors is an integer number (7004006673404).

Almost surely, 2^{21012020020209} is an apocalyptic number.

It is an amenable number.

21012020020209 is a deficient number, since it is larger than the sum of its proper divisors (7004006673407).

21012020020209 is an equidigital number, since it uses as much as digits as its factorization.

21012020020209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7004006673406.

The product of its (nonzero) digits is 288, while the sum is 21.

The spelling of 21012020020209 in words is "twenty-one trillion, twelve billion, twenty million, twenty thousand, two hundred nine".