1221231221 has 16 divisors (see below), whose sum is σ = 1426919424. Its totient is φ = 1023398064.

The previous prime is 1221231203. The next prime is 1221231233. The reversal of 1221231221 is 1221321221.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221231221 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1221231221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221231241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 486656 + ... + 489158.

It is an arithmetic number, because the mean of its divisors is an integer number (89182464).

Almost surely, 2^1221231221 is an apocalyptic number.

It is an amenable number.

1221231221 is a deficient number, since it is larger than the sum of its proper divisors (205688203).

1221231221 is a wasteful number, since it uses less digits than its factorization.

1221231221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4040.

The product of its digits is 96, while the sum is 17.

The square root of 1221231221 is about 34946.1188259870. The cubic root of 1221231221 is about 1068.8890618225.

Adding to 1221231221 its reverse (1221321221), we get a palindrome (2442552442).

Subtracting 1221231221 from its reverse (1221321221), we obtain a square (90000 = 300²).

The spelling of 1221231221 in words is "one billion, two hundred twenty-one million, two hundred thirty-one thousand, two hundred twenty-one".