21201012220021 has 4 divisors (see below), whose sum is σ = 21204287525772. Its totient is φ = 21197736914272.

The previous prime is 21201012219949. The next prime is 21201012220039. The reversal of 21201012220021 is 12002221010212.

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 6247555239121 + 14953456980900 = 2499511^2 + 3866970^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201012220021 - 2¹⁹ = 21201011695733 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21201012219977 and 21201012220004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201012200021) 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, 1637643166 + ... + 1637656111.

It is an arithmetic number, because the mean of its divisors is an integer number (5301071881443).

Almost surely, 2^{21201012220021} is an apocalyptic number.

It is an amenable number.

21201012220021 is a deficient number, since it is larger than the sum of its proper divisors (3275305751).

21201012220021 is an equidigital number, since it uses as much as digits as its factorization.

21201012220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3275305750.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21201012220021 its reverse (12002221010212), we get a palindrome (33203233230233).

The spelling of 21201012220021 in words is "twenty-one trillion, two hundred one billion, twelve million, two hundred twenty thousand, twenty-one".