1221121000021 has 4 divisors (see below), whose sum is σ = 1315053384652. Its totient is φ = 1127188615392.

The previous prime is 1221121000007. The next prime is 1221121000051. The reversal of 1221121000021 is 1200001211221.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 54258714225 + 1166862285796 = 232935^2 + 1080214^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221121000021 - 2¹⁹ = 1221120475733 is a prime.

It is a super-2 number, since 2×1221121000021² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (13), and also a Moran number because the ratio is a prime number: 93932384617 = 1221121000021 / (1 + 2 + 2 + 1 + 1 + 2 + 1 + 0 + 0 + 0 + 0 + 2 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221120999965 and 1221121000010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221121000051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46966192296 + ... + 46966192321.

It is an arithmetic number, because the mean of its divisors is an integer number (328763346163).

Almost surely, 2^{1221121000021} is an apocalyptic number.

It is an amenable number.

1221121000021 is a deficient number, since it is larger than the sum of its proper divisors (93932384631).

1221121000021 is an equidigital number, since it uses as much as digits as its factorization.

1221121000021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93932384630.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 1221121000021 its reverse (1200001211221), we get a palindrome (2421122211242).

The spelling of 1221121000021 in words is "one trillion, two hundred twenty-one billion, one hundred twenty-one million, twenty-one", and thus it is an aban number.