21008135 has 8 divisors (see below), whose sum is σ = 25234800. Its totient is φ = 16789824.

The previous prime is 21008083. The next prime is 21008149. The reversal of 21008135 is 53180012.

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 21008135 - 2⁸ = 21007879 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7259 + ... + 9731.

It is an arithmetic number, because the mean of its divisors is an integer number (3154350).

Almost surely, 2^21008135 is an apocalyptic number.

21008135 is a deficient number, since it is larger than the sum of its proper divisors (4226665).

21008135 is a wasteful number, since it uses less digits than its factorization.

21008135 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4177.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21008135 is about 4583.4632102811. The cubic root of 21008135 is about 275.9280381948.

Adding to 21008135 its reverse (53180012), we get a palindrome (74188147).

The spelling of 21008135 in words is "twenty-one million, eight thousand, one hundred thirty-five".