21056213 has 4 divisors (see below), whose sum is σ = 21068460. Its totient is φ = 21043968.

The previous prime is 21056179. The next prime is 21056227. The reversal of 21056213 is 31265012.

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 8254129 + 12802084 = 2873^2 + 3578^2 .

It is a cyclic number.

It is not a de Polignac number, because 21056213 - 2¹² = 21052117 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056263) 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, 3020 + ... + 7157.

It is an arithmetic number, because the mean of its divisors is an integer number (5267115).

Almost surely, 2^21056213 is an apocalyptic number.

It is an amenable number.

21056213 is a deficient number, since it is larger than the sum of its proper divisors (12247).

21056213 is a wasteful number, since it uses less digits than its factorization.

21056213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12246.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21056213 is about 4588.7049371255. The cubic root of 21056213 is about 276.1383687974.

The spelling of 21056213 in words is "twenty-one million, fifty-six thousand, two hundred thirteen".