21238993 has 4 divisors (see below), whose sum is σ = 21296308. Its totient is φ = 21181680.

The previous prime is 21238981. The next prime is 21239027. The reversal of 21238993 is 39983212.

21238993 is an esthetic number in base 8, because in such base its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11209104 + 10029889 = 3348^2 + 3167^2 .

It is a cyclic number.

It is not a de Polignac number, because 21238993 - 2¹³ = 21230801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21238963) 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, 28098 + ... + 28843.

It is an arithmetic number, because the mean of its divisors is an integer number (5324077).

Almost surely, 2^21238993 is an apocalyptic number.

It is an amenable number.

21238993 is a deficient number, since it is larger than the sum of its proper divisors (57315).

21238993 is an equidigital number, since it uses as much as digits as its factorization.

21238993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57314.

The product of its digits is 23328, while the sum is 37.

The square root of 21238993 is about 4608.5781972318. The cubic root of 21238993 is about 276.9350810343.

The spelling of 21238993 in words is "twenty-one million, two hundred thirty-eight thousand, nine hundred ninety-three".