21004115 has 16 divisors (see below), whose sum is σ = 27586656. Its totient is φ = 15225600.

The previous prime is 21004099. The next prime is 21004117. The reversal of 21004115 is 51140012.

It is not a de Polignac number, because 21004115 - 2⁴ = 21004099 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 21004115.

It is not an unprimeable number, because it can be changed into a prime (21004117) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28289 + ... + 29021.

It is an arithmetic number, because the mean of its divisors is an integer number (1724166).

Almost surely, 2^21004115 is an apocalyptic number.

21004115 is a deficient number, since it is larger than the sum of its proper divisors (6582541).

21004115 is a wasteful number, since it uses less digits than its factorization.

21004115 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1270.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21004115 is about 4583.0246562723. The cubic root of 21004115 is about 275.9104370532.

Adding to 21004115 its reverse (51140012), we get a palindrome (72144127).

The spelling of 21004115 in words is "twenty-one million, four thousand, one hundred fifteen".