21243013 has 16 divisors (see below), whose sum is σ = 25069824. Its totient is φ = 17781760.

The previous prime is 21243011. The next prime is 21243023. The reversal of 21243013 is 31034212.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21243013 - 2¹ = 21243011 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7581 + ... + 9997.

It is an arithmetic number, because the mean of its divisors is an integer number (1566864).

Almost surely, 2^21243013 is an apocalyptic number.

It is an amenable number.

21243013 is a deficient number, since it is larger than the sum of its proper divisors (3826811).

21243013 is a wasteful number, since it uses less digits than its factorization.

21243013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2492.

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

The square root of 21243013 is about 4609.0143197868. The cubic root of 21243013 is about 276.9525521827.

Adding to 21243013 its reverse (31034212), we get a palindrome (52277225).

The spelling of 21243013 in words is "twenty-one million, two hundred forty-three thousand, thirteen".