21135287 has 8 divisors (see below), whose sum is σ = 22278240. Its totient is φ = 20020000.

The previous prime is 21135259. The next prime is 21135293. The reversal of 21135287 is 78253112.

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 21135287 - 2⁶ = 21135223 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135227) 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, 5339 + ... + 8412.

It is an arithmetic number, because the mean of its divisors is an integer number (2784780).

Almost surely, 2^21135287 is an apocalyptic number.

21135287 is a deficient number, since it is larger than the sum of its proper divisors (1142953).

21135287 is a wasteful number, since it uses less digits than its factorization.

21135287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13833.

The product of its digits is 3360, while the sum is 29.

The square root of 21135287 is about 4597.3130195800. The cubic root of 21135287 is about 276.4836048079.

Adding to 21135287 its reverse (78253112), we get a palindrome (99388399).

The spelling of 21135287 in words is "twenty-one million, one hundred thirty-five thousand, two hundred eighty-seven".