21126505 has 4 divisors (see below), whose sum is σ = 25351812. Its totient is φ = 16901200.

The previous prime is 21126487. The next prime is 21126517. The reversal of 21126505 is 50562112.

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 15594601 + 5531904 = 3949^2 + 2352^2 .

It is not a de Polignac number, because 21126505 - 2¹⁹ = 20602217 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

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, 2112646 + ... + 2112655.

It is an arithmetic number, because the mean of its divisors is an integer number (6337953).

Almost surely, 2^21126505 is an apocalyptic number.

It is an amenable number.

21126505 is a deficient number, since it is larger than the sum of its proper divisors (4225307).

21126505 is an equidigital number, since it uses as much as digits as its factorization.

21126505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4225306.

The product of its (nonzero) digits is 600, while the sum is 22.

The square root of 21126505 is about 4596.3577972129. The cubic root of 21126505 is about 276.4453052666.

Adding to 21126505 its reverse (50562112), we get a palindrome (71688617).

The spelling of 21126505 in words is "twenty-one million, one hundred twenty-six thousand, five hundred five".