1221100111 has 16 divisors (see below), whose sum is σ = 1557819648. Its totient is φ = 929376000.

The previous prime is 1221100063. The next prime is 1221100121. The reversal of 1221100111 is 1110011221.

It is not a de Polignac number, because 1221100111 - 2¹⁷ = 1220969039 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221100121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 181090 + ... + 187711.

It is an arithmetic number, because the mean of its divisors is an integer number (97363728).

Almost surely, 2^1221100111 is an apocalyptic number.

1221100111 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1221100111 is a deficient number, since it is larger than the sum of its proper divisors (336719537).

1221100111 is a wasteful number, since it uses less digits than its factorization.

1221100111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 368862.

The product of its (nonzero) digits is 4, while the sum is 10.

The square root of 1221100111 is about 34944.2428877777. The cubic root of 1221100111 is about 1068.8508088807.

Adding to 1221100111 its reverse (1110011221), we get a palindrome (2331111332).

The spelling of 1221100111 in words is "one billion, two hundred twenty-one million, one hundred thousand, one hundred eleven".