1321100021 has 4 divisors (see below), whose sum is σ = 1321922700. Its totient is φ = 1320277344.

The previous prime is 1321100009. The next prime is 1321100041. The reversal of 1321100021 is 1200011231.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1200011231 = 2141 ⋅560491.

It can be written as a sum of positive squares in 2 ways, for example, as 713477521 + 607622500 = 26711^2 + 24650^2 .

It is a cyclic number.

It is not a de Polignac number, because 1321100021 - 2²⁶ = 1253991157 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1321099975 and 1321100011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1321100041) 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, 408926 + ... + 412143.

It is an arithmetic number, because the mean of its divisors is an integer number (330480675).

Almost surely, 2^1321100021 is an apocalyptic number.

It is an amenable number.

1321100021 is a deficient number, since it is larger than the sum of its proper divisors (822679).

1321100021 is an equidigital number, since it uses as much as digits as its factorization.

1321100021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 822678.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 1321100021 is about 36346.9396373340. The cubic root of 1321100021 is about 1097.2659431727.

Adding to 1321100021 its reverse (1200011231), we get a palindrome (2521111252).

The spelling of 1321100021 in words is "one billion, three hundred twenty-one million, one hundred thousand, twenty-one".