1221021221 has 4 divisors (see below), whose sum is σ = 1395452832. Its totient is φ = 1046589612.

The previous prime is 1221021203. The next prime is 1221021223. The reversal of 1221021221 is 1221201221.

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 1221021221 - 2¹⁸ = 1220759077 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1221021196 and 1221021205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221021223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 87215795 + ... + 87215808.

It is an arithmetic number, because the mean of its divisors is an integer number (348863208).

Almost surely, 2^1221021221 is an apocalyptic number.

It is an amenable number.

1221021221 is a deficient number, since it is larger than the sum of its proper divisors (174431611).

1221021221 is an equidigital number, since it uses as much as digits as its factorization.

1221021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174431610.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 1221021221 is about 34943.1140713017. The cubic root of 1221021221 is about 1068.8277904414.

Adding to 1221021221 its reverse (1221201221), we get a palindrome (2442222442).

The spelling of 1221021221 in words is "one billion, two hundred twenty-one million, twenty-one thousand, two hundred twenty-one".