21042313 has 4 divisors (see below), whose sum is σ = 21767940. Its totient is φ = 20316688.

The previous prime is 21042293. The next prime is 21042317. The reversal of 21042313 is 31324012.

It is a happy number.

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 12730624 + 8311689 = 3568^2 + 2883^2 .

It is a cyclic number.

It is not a de Polignac number, because 21042313 - 2²¹ = 18945161 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21042317) 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, 362770 + ... + 362827.

It is an arithmetic number, because the mean of its divisors is an integer number (5441985).

Almost surely, 2^21042313 is an apocalyptic number.

It is an amenable number.

21042313 is a deficient number, since it is larger than the sum of its proper divisors (725627).

21042313 is an equidigital number, since it uses as much as digits as its factorization.

21042313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 725626.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21042313 is about 4587.1900985244. The cubic root of 21042313 is about 276.0775923060.

Adding to 21042313 its reverse (31324012), we get a palindrome (52366325).

The spelling of 21042313 in words is "twenty-one million, forty-two thousand, three hundred thirteen".