21221393 has 4 divisors (see below), whose sum is σ = 21672960. Its totient is φ = 20769828.

The previous prime is 21221383. The next prime is 21221411. The reversal of 21221393 is 39312212.

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 21221393 - 2⁴ = 21221377 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21221303) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 225713 + ... + 225806.

It is an arithmetic number, because the mean of its divisors is an integer number (5418240).

Almost surely, 2^21221393 is an apocalyptic number.

It is an amenable number.

21221393 is a deficient number, since it is larger than the sum of its proper divisors (451567).

21221393 is an equidigital number, since it uses as much as digits as its factorization.

21221393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 451566.

The product of its digits is 648, while the sum is 23.

The square root of 21221393 is about 4606.6683188613. The cubic root of 21221393 is about 276.8585644693.

The spelling of 21221393 in words is "twenty-one million, two hundred twenty-one thousand, three hundred ninety-three".