21380213 has 4 divisors (see below), whose sum is σ = 21488940. Its totient is φ = 21271488.

The previous prime is 21380207. The next prime is 21380257. The reversal of 21380213 is 31208312.

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 20593444 + 786769 = 4538^2 + 887^2 .

It is a cyclic number.

It is not a de Polignac number, because 21380213 - 2⁴ = 21380197 is a prime.

It is a super-2 number, since 2×21380213² = 914227015850738, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21380273) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 54068 + ... + 54461.

It is an arithmetic number, because the mean of its divisors is an integer number (5372235).

Almost surely, 2^21380213 is an apocalyptic number.

It is an amenable number.

21380213 is a deficient number, since it is larger than the sum of its proper divisors (108727).

21380213 is a wasteful number, since it uses less digits than its factorization.

21380213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108726.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21380213 is about 4623.8742413695. The cubic root of 21380213 is about 277.5475145217.

Adding to 21380213 its reverse (31208312), we get a palindrome (52588525).

The spelling of 21380213 in words is "twenty-one million, three hundred eighty thousand, two hundred thirteen".