1311111221 has 4 divisors (see below), whose sum is σ = 1498412832. Its totient is φ = 1123809612.

The previous prime is 1311111211. The next prime is 1311111223. The reversal of 1311111221 is 1221111131.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1221111131 = 6581 ⋅185551.

It is a cyclic number.

It is not a de Polignac number, because 1311111221 - 2¹⁸ = 1310849077 is a prime.

It is a super-2 number, since 2×1311111221² = 3438025267664221682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1311111196 and 1311111205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1311111223) 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, 93650795 + ... + 93650808.

It is an arithmetic number, because the mean of its divisors is an integer number (374603208).

Almost surely, 2^1311111221 is an apocalyptic number.

It is an amenable number.

1311111221 is a deficient number, since it is larger than the sum of its proper divisors (187301611).

1311111221 is an equidigital number, since it uses as much as digits as its factorization.

1311111221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187301610.

The product of its digits is 12, while the sum is 14.

The square root of 1311111221 is about 36209.2698214145. The cubic root of 1311111221 is about 1094.4934782612.

Adding to 1311111221 its reverse (1221111131), we get a palindrome (2532222352).

The spelling of 1311111221 in words is "one billion, three hundred eleven million, one hundred eleven thousand, two hundred twenty-one".