21201001221 has 16 divisors (see below), whose sum is σ = 29440914048. Its totient is φ = 13558305600.

The previous prime is 21201001219. The next prime is 21201001253. The reversal of 21201001221 is 12210010212.

It is not a de Polignac number, because 21201001221 - 2¹ = 21201001219 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21201001197 and 21201001206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201001621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1337190 + ... + 1352951.

It is an arithmetic number, because the mean of its divisors is an integer number (1840057128).

Almost surely, 2^21201001221 is an apocalyptic number.

It is an amenable number.

21201001221 is a deficient number, since it is larger than the sum of its proper divisors (8239912827).

21201001221 is a wasteful number, since it uses less digits than its factorization.

21201001221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2690252.

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

Adding to 21201001221 its reverse (12210010212), we get a palindrome (33411011433).

The spelling of 21201001221 in words is "twenty-one billion, two hundred one million, one thousand, two hundred twenty-one".