1221100001 has 4 divisors (see below), whose sum is σ = 1332109104. Its totient is φ = 1110090900.

The previous prime is 1221099967. The next prime is 1221100033. The reversal of 1221100001 is 1000011221.

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: 1000011221 = 11 ⋅90910111.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221100001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221100901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55504535 + ... + 55504556.

It is an arithmetic number, because the mean of its divisors is an integer number (333027276).

Almost surely, 2^1221100001 is an apocalyptic number.

1221100001 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221100001 is a deficient number, since it is larger than the sum of its proper divisors (111009103).

1221100001 is a wasteful number, since it uses less digits than its factorization.

1221100001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111009102.

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 1221100001 is about 34944.2413138417. The cubic root of 1221100001 is about 1068.8507767857.

Adding to 1221100001 its reverse (1000011221), we get a palindrome (2221111222).

It can be divided in two parts, 1221 and 100001, that multiplied together give a palindrome (122101221).

The spelling of 1221100001 in words is "one billion, two hundred twenty-one million, one hundred thousand, one".