21131393 has 4 divisors (see below), whose sum is σ = 21271488. Its totient is φ = 20991300.

The previous prime is 21131389. The next prime is 21131399. The reversal of 21131393 is 39313112.

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 21131393 - 2² = 21131389 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131399) 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, 69821 + ... + 70122.

It is an arithmetic number, because the mean of its divisors is an integer number (5317872).

Almost surely, 2^21131393 is an apocalyptic number.

It is an amenable number.

21131393 is a deficient number, since it is larger than the sum of its proper divisors (140095).

21131393 is a wasteful number, since it uses less digits than its factorization.

21131393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140094.

The product of its digits is 486, while the sum is 23.

The square root of 21131393 is about 4596.8894918194. The cubic root of 21131393 is about 276.4666238338.

The spelling of 21131393 in words is "twenty-one million, one hundred thirty-one thousand, three hundred ninety-three".