21213361 has 4 divisors (see below), whose sum is σ = 22845172. Its totient is φ = 19581552.

The previous prime is 21213349. The next prime is 21213373. The reversal of 21213361 is 16331212.

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

It is an interprime number because it is at equal distance from previous prime (21213349) and next prime (21213373).

It can be written as a sum of positive squares in 2 ways, for example, as 2421136 + 18792225 = 1556^2 + 4335^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213361 - 2¹³ = 21205169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21213341) 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, 815886 + ... + 815911.

It is an arithmetic number, because the mean of its divisors is an integer number (5711293).

Almost surely, 2^21213361 is an apocalyptic number.

It is an amenable number.

21213361 is a deficient number, since it is larger than the sum of its proper divisors (1631811).

21213361 is a wasteful number, since it uses less digits than its factorization.

21213361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1631810.

The product of its digits is 216, while the sum is 19.

The square root of 21213361 is about 4605.7964566403. The cubic root of 21213361 is about 276.8236310321.

Adding to 21213361 its reverse (16331212), we get a palindrome (37544573).

The spelling of 21213361 in words is "twenty-one million, two hundred thirteen thousand, three hundred sixty-one".