1221202221 has 4 divisors (see below), whose sum is σ = 1628269632. Its totient is φ = 814134812.

The previous prime is 1221202183. The next prime is 1221202223. The reversal of 1221202221 is 1222021221.

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 a de Polignac number, because none of the positive numbers 2^k-1221202221 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 1221202221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221202223) 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, 203533701 + ... + 203533706.

It is an arithmetic number, because the mean of its divisors is an integer number (407067408).

Almost surely, 2^1221202221 is an apocalyptic number.

It is an amenable number.

1221202221 is a deficient number, since it is larger than the sum of its proper divisors (407067411).

1221202221 is an equidigital number, since it uses as much as digits as its factorization.

1221202221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 407067410.

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

The square root of 1221202221 is about 34945.7038990489. The cubic root of 1221202221 is about 1068.8806009546.

Adding to 1221202221 its reverse (1222021221), we get a palindrome (2443223442).

The spelling of 1221202221 in words is "one billion, two hundred twenty-one million, two hundred two thousand, two hundred twenty-one".