21266005 has 4 divisors (see below), whose sum is σ = 25519212. Its totient is φ = 17012800.

The previous prime is 21265999. The next prime is 21266017. The reversal of 21266005 is 50066212.

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 3617604 + 17648401 = 1902^2 + 4201^2 .

It is not a de Polignac number, because 21266005 - 2⁷ = 21265877 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 a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2126596 + ... + 2126605.

It is an arithmetic number, because the mean of its divisors is an integer number (6379803).

Almost surely, 2^21266005 is an apocalyptic number.

It is an amenable number.

21266005 is a deficient number, since it is larger than the sum of its proper divisors (4253207).

21266005 is an equidigital number, since it uses as much as digits as its factorization.

21266005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4253206.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21266005 is about 4611.5078878822. The cubic root of 21266005 is about 277.0524343909.

The spelling of 21266005 in words is "twenty-one million, two hundred sixty-six thousand, five".