21026213 has 8 divisors (see below), whose sum is σ = 23071608. Its totient is φ = 19041984.

The previous prime is 21026197. The next prime is 21026231. The reversal of 21026213 is 31262012.

It can be written as a sum of positive squares in 4 ways, for example, as 77284 + 20948929 = 278^2 + 4577^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21026213 - 2⁴ = 21026197 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21026191 and 21026200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21022213) 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 7 ways as a sum of consecutive naturals, for example, 14570 + ... + 15947.

It is an arithmetic number, because the mean of its divisors is an integer number (2883951).

Almost surely, 2^21026213 is an apocalyptic number.

It is an amenable number.

21026213 is a deficient number, since it is larger than the sum of its proper divisors (2045395).

21026213 is a wasteful number, since it uses less digits than its factorization.

21026213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30583.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 21026213 is about 4585.4348757779. The cubic root of 21026213 is about 276.0071630501.

Adding to 21026213 its reverse (31262012), we get a palindrome (52288225).

The spelling of 21026213 in words is "twenty-one million, twenty-six thousand, two hundred thirteen".