21243015 has 12 divisors (see below), whose sum is σ = 36821304. Its totient is φ = 11329584.

The previous prime is 21243011. The next prime is 21243023. The reversal of 21243015 is 51034212.

It is not a de Polignac number, because 21243015 - 2² = 21243011 is a prime.

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 11 ways as a sum of consecutive naturals, for example, 235989 + ... + 236078.

It is an arithmetic number, because the mean of its divisors is an integer number (3068442).

Almost surely, 2^21243015 is an apocalyptic number.

21243015 is a deficient number, since it is larger than the sum of its proper divisors (15578289).

21243015 is a wasteful number, since it uses less digits than its factorization.

21243015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472078 (or 472075 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21243015 is about 4609.0145367529. The cubic root of 21243015 is about 276.9525608743.

Adding to 21243015 its reverse (51034212), we get a palindrome (72277227).

The spelling of 21243015 in words is "twenty-one million, two hundred forty-three thousand, fifteen".