21146915 has 4 divisors (see below), whose sum is σ = 25376304. Its totient is φ = 16917528.

The previous prime is 21146911. The next prime is 21146921. The reversal of 21146915 is 51964112.

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 21146915 - 2² = 21146911 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21146911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2114687 + ... + 2114696.

It is an arithmetic number, because the mean of its divisors is an integer number (6344076).

Almost surely, 2^21146915 is an apocalyptic number.

21146915 is a deficient number, since it is larger than the sum of its proper divisors (4229389).

21146915 is an equidigital number, since it uses as much as digits as its factorization.

21146915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4229388.

The product of its digits is 2160, while the sum is 29.

The square root of 21146915 is about 4598.5774974442. The cubic root of 21146915 is about 276.5342998367.

The spelling of 21146915 in words is "twenty-one million, one hundred forty-six thousand, nine hundred fifteen".