21135605 has 8 divisors (see below), whose sum is σ = 25841592. Its totient is φ = 16589248.

The previous prime is 21135593. The next prime is 21135613. The reversal of 21135605 is 50653112.

It can be written as a sum of positive squares in 4 ways, for example, as 5207524 + 15928081 = 2282^2 + 3991^2 .

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 21135605 - 2⁴ = 21135589 is a prime.

It is a Duffinian number.

It is a zygodrome in base 4.

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, 39614 + ... + 40143.

It is an arithmetic number, because the mean of its divisors is an integer number (3230199).

Almost surely, 2^21135605 is an apocalyptic number.

It is an amenable number.

21135605 is a deficient number, since it is larger than the sum of its proper divisors (4705987).

21135605 is an equidigital number, since it uses as much as digits as its factorization.

21135605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79815.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21135605 is about 4597.3476048696. The cubic root of 21135605 is about 276.4849914518.

Adding to 21135605 its reverse (50653112), we get a palindrome (71788717).

The spelling of 21135605 in words is "twenty-one million, one hundred thirty-five thousand, six hundred five".