21166213 has 4 divisors (see below), whose sum is σ = 21284640. Its totient is φ = 21047788.

The previous prime is 21166199. The next prime is 21166217. The reversal of 21166213 is 31266112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21166213 - 2⁵ = 21166181 is a prime.

It is a super-2 number, since 2×21166213² = 896017145522738, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166217) 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, 58945 + ... + 59302.

It is an arithmetic number, because the mean of its divisors is an integer number (5321160).

Almost surely, 2^21166213 is an apocalyptic number.

It is an amenable number.

21166213 is a deficient number, since it is larger than the sum of its proper divisors (118427).

21166213 is a wasteful number, since it uses less digits than its factorization.

21166213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118426.

The product of its digits is 432, while the sum is 22.

The square root of 21166213 is about 4600.6752765219. The cubic root of 21166213 is about 276.6183930550.

The spelling of 21166213 in words is "twenty-one million, one hundred sixty-six thousand, two hundred thirteen".