21093821 has 12 divisors (see below), whose sum is σ = 25611168. Its totient is φ = 17015232.

The previous prime is 21093799. The next prime is 21093833. The reversal of 21093821 is 12839012.

It is not a de Polignac number, because 21093821 - 2⁶ = 21093757 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 (21092821) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3191 + ... + 7236.

It is an arithmetic number, because the mean of its divisors is an integer number (2134264).

Almost surely, 2^21093821 is an apocalyptic number.

It is an amenable number.

21093821 is a deficient number, since it is larger than the sum of its proper divisors (4517347).

21093821 is a wasteful number, since it uses less digits than its factorization.

21093821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10468 (or 10451 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21093821 is about 4592.8009972129. The cubic root of 21093821 is about 276.3026724021.

The spelling of 21093821 in words is "twenty-one million, ninety-three thousand, eight hundred twenty-one".