21216135 has 8 divisors (see below), whose sum is σ = 33945840. Its totient is φ = 11315264.

The previous prime is 21216127. The next prime is 21216137. The reversal of 21216135 is 53161212.

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

It is a cyclic number.

It is not a de Polignac number, because 21216135 - 2³ = 21216127 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216137) 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, 707190 + ... + 707219.

It is an arithmetic number, because the mean of its divisors is an integer number (4243230).

Almost surely, 2^21216135 is an apocalyptic number.

21216135 is a deficient number, since it is larger than the sum of its proper divisors (12729705).

21216135 is a wasteful number, since it uses less digits than its factorization.

21216135 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1414417.

The product of its digits is 360, while the sum is 21.

The square root of 21216135 is about 4606.0975890660. The cubic root of 21216135 is about 276.8356969385.

Adding to 21216135 its reverse (53161212), we get a palindrome (74377347).

It can be divided in two parts, 2121 and 6135, that added together give a triangular number (8256 = T₁₂₈).

The spelling of 21216135 in words is "twenty-one million, two hundred sixteen thousand, one hundred thirty-five".