1211220221 has 4 divisors (see below), whose sum is σ = 1236990912. Its totient is φ = 1185449532.

The previous prime is 1211220217. The next prime is 1211220223. The reversal of 1211220221 is 1220221121.

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 1211220221 - 2² = 1211220217 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 = 1211220196 and 1211220205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211220223) 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, 12885275 + ... + 12885368.

It is an arithmetic number, because the mean of its divisors is an integer number (309247728).

Almost surely, 2^1211220221 is an apocalyptic number.

It is an amenable number.

1211220221 is a deficient number, since it is larger than the sum of its proper divisors (25770691).

1211220221 is an equidigital number, since it uses as much as digits as its factorization.

1211220221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25770690.

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

The square root of 1211220221 is about 34802.5892858563. The cubic root of 1211220221 is about 1065.9603175895.

Adding to 1211220221 its reverse (1220221121), we get a palindrome (2431441342).

It can be divided in two parts, 121 and 1220221, that multiplied together give a palindrome (147646741).

The spelling of 1211220221 in words is "one billion, two hundred eleven million, two hundred twenty thousand, two hundred twenty-one".