1221111011 has 4 divisors (see below), whose sum is σ = 1225519632. Its totient is φ = 1216702392.

The previous prime is 1221111007. The next prime is 1221111029. The reversal of 1221111011 is 1101111221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1101111221 = 7 ⋅157301603.

It is a cyclic number.

It is not a de Polignac number, because 1221111011 - 2² = 1221111007 is a prime.

It is a super-2 number, since 2×1221111011² = 2982224202370884242, 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 = 1221110983 and 1221111001.

It is not an unprimeable number, because it can be changed into a prime (1221111511) 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, 2203895 + ... + 2204448.

It is an arithmetic number, because the mean of its divisors is an integer number (306379908).

Almost surely, 2^1221111011 is an apocalyptic number.

1221111011 is a deficient number, since it is larger than the sum of its proper divisors (4408621).

1221111011 is an equidigital number, since it uses as much as digits as its factorization.

1221111011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4408620.

The product of its (nonzero) digits is 4, while the sum is 11.

The square root of 1221111011 is about 34944.3988501734. The cubic root of 1221111011 is about 1068.8539891930.

Adding to 1221111011 its reverse (1101111221), we get a palindrome (2322222232).

The spelling of 1221111011 in words is "one billion, two hundred twenty-one million, one hundred eleven thousand, eleven".