1221320221 has 4 divisors (see below), whose sum is σ = 1332349344. Its totient is φ = 1110291100.

The previous prime is 1221320197. The next prime is 1221320227. The reversal of 1221320221 is 1220231221.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1221320221 - 2⁹ = 1221319709 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221320195 and 1221320204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221320227) 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 3 ways as a sum of consecutive naturals, for example, 55514545 + ... + 55514566.

It is an arithmetic number, because the mean of its divisors is an integer number (333087336).

Almost surely, 2^1221320221 is an apocalyptic number.

1221320221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221320221 is a deficient number, since it is larger than the sum of its proper divisors (111029123).

1221320221 is a wasteful number, since it uses less digits than its factorization.

1221320221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111029122.

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 1221320221 is about 34947.3921916929. The cubic root of 1221320221 is about 1068.9150270981.

Adding to 1221320221 its reverse (1220231221), we get a palindrome (2441551442).

The spelling of 1221320221 in words is "one billion, two hundred twenty-one million, three hundred twenty thousand, two hundred twenty-one".