21366213 has 16 divisors (see below), whose sum is σ = 31159296. Its totient is φ = 12915440.

The previous prime is 21366197. The next prime is 21366221. The reversal of 21366213 is 31266312.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21366213 - 2⁴ = 21366197 is a prime.

It is a super-2 number, since 2×21366213² = 913030115922738, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21366113) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18820 + ... + 19922.

It is an arithmetic number, because the mean of its divisors is an integer number (1947456).

Almost surely, 2^21366213 is an apocalyptic number.

It is an amenable number.

21366213 is a deficient number, since it is larger than the sum of its proper divisors (9793083).

21366213 is a wasteful number, since it uses less digits than its factorization.

21366213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1704.

The product of its digits is 1296, while the sum is 24.

The square root of 21366213 is about 4622.3601114582. The cubic root of 21366213 is about 277.4869208997.

Subtracting 21366213 from its reverse (31266312), we obtain a palindrome (9900099).

The spelling of 21366213 in words is "twenty-one million, three hundred sixty-six thousand, two hundred thirteen".