21001201221 has 64 divisors (see below), whose sum is σ = 38612883456. Its totient is φ = 9798278400.

The previous prime is 21001201159. The next prime is 21001201231. The reversal of 21001201221 is 12210210012.

It is not a de Polignac number, because 21001201221 - 2⁶ = 21001201157 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001201197 and 21001201206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001201231) 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 63 ways as a sum of consecutive naturals, for example, 16606 + ... + 205616.

It is an arithmetic number, because the mean of its divisors is an integer number (603326304).

Almost surely, 2^21001201221 is an apocalyptic number.

21001201221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21001201221 is a deficient number, since it is larger than the sum of its proper divisors (17611682235).

21001201221 is a wasteful number, since it uses less digits than its factorization.

21001201221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189082.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001201221 its reverse (12210210012), we get a palindrome (33211411233).

It can be divided in two parts, 21001 and 201221, that added together give a palindrome (222222).

The spelling of 21001201221 in words is "twenty-one billion, one million, two hundred one thousand, two hundred twenty-one".