21280845 has 16 divisors (see below), whose sum is σ = 34880832. Its totient is φ = 11072640.

The previous prime is 21280843. The next prime is 21280873. The reversal of 21280845 is 54808212.

It is not a de Polignac number, because 21280845 - 2¹ = 21280843 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16687 + ... + 17916.

It is an arithmetic number, because the mean of its divisors is an integer number (2180052).

Almost surely, 2^21280845 is an apocalyptic number.

It is an amenable number.

21280845 is a deficient number, since it is larger than the sum of its proper divisors (13599987).

21280845 is a wasteful number, since it uses less digits than its factorization.

21280845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34652.

The product of its (nonzero) digits is 5120, while the sum is 30.

The square root of 21280845 is about 4613.1166254497. The cubic root of 21280845 is about 277.1168643286.

The spelling of 21280845 in words is "twenty-one million, two hundred eighty thousand, eight hundred forty-five".