21013213 has 4 divisors (see below), whose sum is σ = 22629628. Its totient is φ = 19396800.

The previous prime is 21013189. The next prime is 21013217. The reversal of 21013213 is 31231012.

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 5631129 + 15382084 = 2373^2 + 3922^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013213 - 2⁹ = 21012701 is a prime.

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: 1616401 = 21013213 / (2 + 1 + 0 + 1 + 3 + 2 + 1 + 3).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21013193 and 21013202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013217) 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, 808188 + ... + 808213.

It is an arithmetic number, because the mean of its divisors is an integer number (5657407).

Almost surely, 2^21013213 is an apocalyptic number.

It is an amenable number.

21013213 is a deficient number, since it is larger than the sum of its proper divisors (1616415).

21013213 is a wasteful number, since it uses less digits than its factorization.

21013213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1616414.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21013213 is about 4584.0171247499. The cubic root of 21013213 is about 275.9502684673.

Adding to 21013213 its reverse (31231012), we get a palindrome (52244225).

The spelling of 21013213 in words is "twenty-one million, thirteen thousand, two hundred thirteen".