21231393 has 16 divisors (see below), whose sum is σ = 29694720. Its totient is φ = 13474944.

The previous prime is 21231391. The next prime is 21231403. The reversal of 21231393 is 39313212.

It is not a de Polignac number, because 21231393 - 2¹ = 21231391 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21231391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4680 + ... + 8022.

It is an arithmetic number, because the mean of its divisors is an integer number (1855920).

Almost surely, 2^21231393 is an apocalyptic number.

It is an amenable number.

21231393 is a deficient number, since it is larger than the sum of its proper divisors (8463327).

21231393 is a wasteful number, since it uses less digits than its factorization.

21231393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3448.

The product of its digits is 972, while the sum is 24.

The square root of 21231393 is about 4607.7535741400. The cubic root of 21231393 is about 276.9020449780.

The spelling of 21231393 in words is "twenty-one million, two hundred thirty-one thousand, three hundred ninety-three".