1211223121 has 4 divisors (see below), whose sum is σ = 1211292772. Its totient is φ = 1211153472.

The previous prime is 1211223113. The next prime is 1211223133. The reversal of 1211223121 is 1213221121.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1005587521 + 205635600 = 31711^2 + 14340^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211223121 - 2³ = 1211223113 is a prime.

It is a super-2 number, since 2×1211223121² = 2934122897689961282, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1211223095 and 1211223104.

It is not an unprimeable number, because it can be changed into a prime (1211223421) 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, 15541 + ... + 51613.

It is an arithmetic number, because the mean of its divisors is an integer number (302823193).

Almost surely, 2^1211223121 is an apocalyptic number.

It is an amenable number.

1211223121 is a deficient number, since it is larger than the sum of its proper divisors (69651).

1211223121 is an equidigital number, since it uses as much as digits as its factorization.

1211223121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69650.

The product of its digits is 48, while the sum is 16.

The square root of 1211223121 is about 34802.6309493981. The cubic root of 1211223121 is about 1065.9611683245.

Adding to 1211223121 its reverse (1213221121), we get a palindrome (2424444242).

The spelling of 1211223121 in words is "one billion, two hundred eleven million, two hundred twenty-three thousand, one hundred twenty-one".