21266213 has 2 divisors, whose sum is σ = 21266214. Its totient is φ = 21266212.

The previous prime is 21266207. The next prime is 21266239. The reversal of 21266213 is 31266212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21141604 + 124609 = 4598^2 + 353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21266213 - 2⁸ = 21265957 is a prime.

It is a super-2 number, since 2×21266213² = 904503630722738, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21266293) 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 as a sum of consecutive naturals, namely, 10633106 + 10633107.

It is an arithmetic number, because the mean of its divisors is an integer number (10633107).

Almost surely, 2^21266213 is an apocalyptic number.

It is an amenable number.

21266213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21266213 is an equidigital number, since it uses as much as digits as its factorization.

21266213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 23.

The square root of 21266213 is about 4611.5304401034. The cubic root of 21266213 is about 277.0533376591.

Subtracting 21266213 from its reverse (31266212), we obtain a palindrome (9999999).

The spelling of 21266213 in words is "twenty-one million, two hundred sixty-six thousand, two hundred thirteen".