21266505 has 24 divisors (see below), whose sum is σ = 39698568. Its totient is φ = 10469376.

The previous prime is 21266503. The next prime is 21266519. The reversal of 21266505 is 50566212.

21266505 is a `hidden beast` number, since 2 + 1 + 2 + 6 + 650 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 5184 + 21261321 = 72^2 + 4611^2 .

It is not a de Polignac number, because 21266505 - 2¹ = 21266503 is a prime.

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (21266503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17592 + ... + 18761.

It is an arithmetic number, because the mean of its divisors is an integer number (1654107).

Almost surely, 2^21266505 is an apocalyptic number.

It is an amenable number.

21266505 is a deficient number, since it is larger than the sum of its proper divisors (18432063).

21266505 is a wasteful number, since it uses less digits than its factorization.

21266505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36377 (or 36374 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 21266505 is about 4611.5620997662. The cubic root of 21266505 is about 277.0546056987.

The spelling of 21266505 in words is "twenty-one million, two hundred sixty-six thousand, five hundred five".