21215135 has 8 divisors (see below), whose sum is σ = 25644816. Its totient is φ = 16847680.

The previous prime is 21215111. The next prime is 21215137. The reversal of 21215135 is 53151212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21215135 - 2¹⁰ = 21214111 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21215137) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14801 + ... + 16170.

It is an arithmetic number, because the mean of its divisors is an integer number (3205602).

Almost surely, 2^21215135 is an apocalyptic number.

21215135 is a deficient number, since it is larger than the sum of its proper divisors (4429681).

21215135 is a wasteful number, since it uses less digits than its factorization.

21215135 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31113.

The product of its digits is 300, while the sum is 20.

The square root of 21215135 is about 4605.9890360269. The cubic root of 21215135 is about 276.8313474179.

Adding to 21215135 its reverse (53151212), we get a palindrome (74366347).

The spelling of 21215135 in words is "twenty-one million, two hundred fifteen thousand, one hundred thirty-five".