21115015 has 4 divisors (see below), whose sum is σ = 25338024. Its totient is φ = 16892008.

The previous prime is 21115013. The next prime is 21115027. The reversal of 21115015 is 51051112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21115015 - 2¹ = 21115013 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21115015.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21115013) 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, 2111497 + ... + 2111506.

It is an arithmetic number, because the mean of its divisors is an integer number (6334506).

Almost surely, 2^21115015 is an apocalyptic number.

21115015 is a deficient number, since it is larger than the sum of its proper divisors (4223009).

21115015 is an equidigital number, since it uses as much as digits as its factorization.

21115015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4223008.

The product of its (nonzero) digits is 50, while the sum is 16.

The square root of 21115015 is about 4595.1077245262. The cubic root of 21115015 is about 276.3951797241.

Adding to 21115015 its reverse (51051112), we get a palindrome (72166127).

The spelling of 21115015 in words is "twenty-one million, one hundred fifteen thousand, fifteen".