1221220221 has 16 divisors (see below), whose sum is σ = 1770577536. Its totient is φ = 744221376.

The previous prime is 1221220199. The next prime is 1221220229. The reversal of 1221220221 is 1220221221.

It is not a de Polignac number, because 1221220221 - 2¹³ = 1221212029 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1221220221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221220229) 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 15 ways as a sum of consecutive naturals, for example, 147990 + ... + 156023.

It is an arithmetic number, because the mean of its divisors is an integer number (110661096).

Almost surely, 2^1221220221 is an apocalyptic number.

It is an amenable number.

1221220221 is a deficient number, since it is larger than the sum of its proper divisors (549357315).

1221220221 is a wasteful number, since it uses less digits than its factorization.

1221220221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304132.

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 1221220221 is about 34945.9614404869. The cubic root of 1221220221 is about 1068.8858525435.

Adding to 1221220221 its reverse (1220221221), we get a palindrome (2441441442).

The spelling of 1221220221 in words is "one billion, two hundred twenty-one million, two hundred twenty thousand, two hundred twenty-one".