1211212111 has 4 divisors (see below), whose sum is σ = 1225805112. Its totient is φ = 1196619112.

The previous prime is 1211212063. The next prime is 1211212117. The reversal of 1211212111 is 1112121121.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1112121121 = 3517 ⋅316213.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1211212111 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1211212091 and 1211212100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211212117) 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 3 ways as a sum of consecutive naturals, for example, 7296376 + ... + 7296541.

It is an arithmetic number, because the mean of its divisors is an integer number (306451278).

Almost surely, 2^1211212111 is an apocalyptic number.

1211212111 is a deficient number, since it is larger than the sum of its proper divisors (14593001).

1211212111 is an equidigital number, since it uses as much as digits as its factorization.

1211212111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14593000.

The product of its digits is 8, while the sum is 13.

The square root of 1211212111 is about 34802.4727713420. The cubic root of 1211212111 is about 1065.9579384577.

Adding to 1211212111 its reverse (1112121121), we get a palindrome (2323333232).

It can be divided in two parts, 1 and 211212111, that added together give a palindrome (211212112).

The spelling of 1211212111 in words is "one billion, two hundred eleven million, two hundred twelve thousand, one hundred eleven".