21135445 has 4 divisors (see below), whose sum is σ = 25362540. Its totient is φ = 16908352.

The previous prime is 21135431. The next prime is 21135449. The reversal of 21135445 is 54453112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 13373649 + 7761796 = 3657^2 + 2786^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135445 - 2¹⁵ = 21102677 is a prime.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135449) 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, 2113540 + ... + 2113549.

It is an arithmetic number, because the mean of its divisors is an integer number (6340635).

Almost surely, 2^21135445 is an apocalyptic number.

It is an amenable number.

21135445 is a deficient number, since it is larger than the sum of its proper divisors (4227095).

21135445 is an equidigital number, since it uses as much as digits as its factorization.

21135445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4227094.

The product of its digits is 2400, while the sum is 25.

The square root of 21135445 is about 4597.3302034985. The cubic root of 21135445 is about 276.4842937711.

Adding to 21135445 its reverse (54453112), we get a palindrome (75588557).

The spelling of 21135445 in words is "twenty-one million, one hundred thirty-five thousand, four hundred forty-five".