21020121011209 has 4 divisors (see below), whose sum is σ = 21027909128400. Its totient is φ = 21012332894020.

The previous prime is 21020121011189. The next prime is 21020121011269. The reversal of 21020121011209 is 90211012102012.

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 a cyclic number.

It is not a de Polignac number, because 21020121011209 - 2²¹ = 21020118914057 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21020121011209.

It is not an unprimeable number, because it can be changed into a prime (21020121011269) 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, 3894054547 + ... + 3894059944.

It is an arithmetic number, because the mean of its divisors is an integer number (5256977282100).

Almost surely, 2^{21020121011209} is an apocalyptic number.

It is an amenable number.

21020121011209 is a deficient number, since it is larger than the sum of its proper divisors (7788117191).

21020121011209 is an equidigital number, since it uses as much as digits as its factorization.

21020121011209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7788117190.

The product of its (nonzero) digits is 144, while the sum is 22.

The spelling of 21020121011209 in words is "twenty-one trillion, twenty billion, one hundred twenty-one million, eleven thousand, two hundred nine".