21052145 has 4 divisors (see below), whose sum is σ = 25262580. Its totient is φ = 16841712.

The previous prime is 21052127. The next prime is 21052159. The reversal of 21052145 is 54125012.

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 7795264 + 13256881 = 2792^2 + 3641^2 .

It is a cyclic number.

It is not a de Polignac number, because 21052145 - 2⁶ = 21052081 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2105210 + ... + 2105219.

It is an arithmetic number, because the mean of its divisors is an integer number (6315645).

Almost surely, 2^21052145 is an apocalyptic number.

It is an amenable number.

21052145 is a deficient number, since it is larger than the sum of its proper divisors (4210435).

21052145 is an equidigital number, since it uses as much as digits as its factorization.

21052145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4210434.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21052145 is about 4588.2616533934. The cubic root of 21052145 is about 276.1205846049.

Adding to 21052145 its reverse (54125012), we get a palindrome (75177157).

The spelling of 21052145 in words is "twenty-one million, fifty-two thousand, one hundred forty-five".