21135887 has 4 divisors (see below), whose sum is σ = 21451416. Its totient is φ = 20820360.

The previous prime is 21135857. The next prime is 21135889. The reversal of 21135887 is 78853112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21135887 - 2⁶ = 21135823 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 (21135889) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 157664 + ... + 157797.

It is an arithmetic number, because the mean of its divisors is an integer number (5362854).

Almost surely, 2^21135887 is an apocalyptic number.

21135887 is a deficient number, since it is larger than the sum of its proper divisors (315529).

21135887 is an equidigital number, since it uses as much as digits as its factorization.

21135887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 315528.

The product of its digits is 13440, while the sum is 35.

The square root of 21135887 is about 4597.3782746257. The cubic root of 21135887 is about 276.4862211054.

Adding to 21135887 its reverse (78853112), we get a palindrome (99988999).

It can be divided in two parts, 21135 and 887, that added together give a palindrome (22022).

The spelling of 21135887 in words is "twenty-one million, one hundred thirty-five thousand, eight hundred eighty-seven".