21010020121009 has 4 divisors (see below), whose sum is σ = 21010151047540. Its totient is φ = 21009889194480.

The previous prime is 21010020120989. The next prime is 21010020121067. The reversal of 21010020121009 is 90012102001012.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 9695576067984 + 11314444053025 = 3113772^2 + 3363695^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010020121009 - 2⁹ = 21010020120497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21010020121609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65222262 + ... + 65543599.

It is an arithmetic number, because the mean of its divisors is an integer number (5252537761885).

Almost surely, 2^{21010020121009} is an apocalyptic number.

It is an amenable number.

21010020121009 is a deficient number, since it is larger than the sum of its proper divisors (130926531).

21010020121009 is a wasteful number, since it uses less digits than its factorization.

21010020121009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130926530.

The product of its (nonzero) digits is 72, while the sum is 19.

The spelling of 21010020121009 in words is "twenty-one trillion, ten billion, twenty million, one hundred twenty-one thousand, nine".