21135155 has 4 divisors (see below), whose sum is σ = 25362192. Its totient is φ = 16908120.

The previous prime is 21135151. The next prime is 21135161. The reversal of 21135155 is 55153112.

It is a happy number.

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

It is not a de Polignac number, because 21135155 - 2² = 21135151 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21135155.

It is not an unprimeable number, because it can be changed into a prime (21135151) 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, 2113511 + ... + 2113520.

It is an arithmetic number, because the mean of its divisors is an integer number (6340548).

Almost surely, 2^21135155 is an apocalyptic number.

21135155 is a deficient number, since it is larger than the sum of its proper divisors (4227037).

21135155 is an equidigital number, since it uses as much as digits as its factorization.

21135155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4227036.

The product of its digits is 750, while the sum is 23.

The square root of 21135155 is about 4597.2986633457. The cubic root of 21135155 is about 276.4830292159.

Adding to 21135155 its reverse (55153112), we get a palindrome (76288267).

The spelling of 21135155 in words is "twenty-one million, one hundred thirty-five thousand, one hundred fifty-five".