1221120021 has 24 divisors (see below), whose sum is σ = 1819001632. Its totient is φ = 727927200.

The previous prime is 1221120011. The next prime is 1221120029. The reversal of 1221120021 is 1200211221.

It is not a de Polignac number, because 1221120021 - 2¹⁷ = 1220988949 is a prime.

It is a super-2 number, since 2×1221120021² = 2982268211374080882, 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 = 1221119979 and 1221120006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221120029) 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 23 ways as a sum of consecutive naturals, for example, 5431 + ... + 49716.

Almost surely, 2^1221120021 is an apocalyptic number.

1221120021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221120021 is a deficient number, since it is larger than the sum of its proper divisors (597881611).

1221120021 is a wasteful number, since it uses less digits than its factorization.

1221120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55233 (or 55222 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 1221120021 is about 34944.5277690227. The cubic root of 1221120021 is about 1068.8566180424.

Adding to 1221120021 its reverse (1200211221), we get a palindrome (2421331242).

It can be divided in two parts, 12211200 and 21, that added together give a palindrome (12211221).

The spelling of 1221120021 in words is "one billion, two hundred twenty-one million, one hundred twenty thousand, twenty-one".