201721221 has 12 divisors (see below), whose sum is σ = 313788748. Its totient is φ = 124136064.

The previous prime is 201721199. The next prime is 201721231. The reversal of 201721221 is 122127102.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 137945025 + 63776196 = 11745^2 + 7986^2 .

It is not a de Polignac number, because 201721221 - 2⁹ = 201720709 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 201721194 and 201721203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (201721231) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 861940 + ... + 862173.

Almost surely, 2^201721221 is an apocalyptic number.

It is an amenable number.

201721221 is a deficient number, since it is larger than the sum of its proper divisors (112067527).

201721221 is a wasteful number, since it uses less digits than its factorization.

201721221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1724132 (or 1724129 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 201721221 is about 14202.8596064314. The cubic root of 201721221 is about 586.4763848220.

Adding to 201721221 its reverse (122127102), we get a palindrome (323848323).

The spelling of 201721221 in words is "two hundred one million, seven hundred twenty-one thousand, two hundred twenty-one".