21266645 has 4 divisors (see below), whose sum is σ = 25519980. Its totient is φ = 17013312.

The previous prime is 21266633. The next prime is 21266669. The reversal of 21266645 is 54666212.

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 11444689 + 9821956 = 3383^2 + 3134^2 .

It is a cyclic number.

It is not a de Polignac number, because 21266645 - 2⁴ = 21266629 is a prime.

It is a Curzon number.

It is a congruent 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, 2126660 + ... + 2126669.

It is an arithmetic number, because the mean of its divisors is an integer number (6379995).

Almost surely, 2^21266645 is an apocalyptic number.

It is an amenable number.

21266645 is a deficient number, since it is larger than the sum of its proper divisors (4253335).

21266645 is an equidigital number, since it uses as much as digits as its factorization.

21266645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4253334.

The product of its digits is 17280, while the sum is 32.

The square root of 21266645 is about 4611.5772789795. The cubic root of 21266645 is about 277.0552136588.

It can be divided in two parts, 2126 and 6645, that multiplied together give a triangular number (14127270 = T₅₃₁₅).

The spelling of 21266645 in words is "twenty-one million, two hundred sixty-six thousand, six hundred forty-five".