21309135 has 16 divisors (see below), whose sum is σ = 34927200. Its totient is φ = 11087360.

The previous prime is 21309133. The next prime is 21309179. The reversal of 21309135 is 53190312.

It is a happy number.

It is not a de Polignac number, because 21309135 - 2¹ = 21309133 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21309133) 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, 16710 + ... + 17939.

It is an arithmetic number, because the mean of its divisors is an integer number (2182950).

Almost surely, 2^21309135 is an apocalyptic number.

21309135 is a deficient number, since it is larger than the sum of its proper divisors (13618065).

21309135 is a wasteful number, since it uses less digits than its factorization.

21309135 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34698.

The product of its (nonzero) digits is 810, while the sum is 24.

The square root of 21309135 is about 4616.1818638351. The cubic root of 21309135 is about 277.2396063962.

Adding to 21309135 its reverse (53190312), we get a palindrome (74499447).

The spelling of 21309135 in words is "twenty-one million, three hundred nine thousand, one hundred thirty-five".