21280863 has 4 divisors (see below), whose sum is σ = 28374488. Its totient is φ = 14187240.

The previous prime is 21280843. The next prime is 21280873. The reversal of 21280863 is 36808212.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21280863 - 2¹² = 21276767 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21280863.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280823) by changing a digit.

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, 3546808 + ... + 3546813.

It is an arithmetic number, because the mean of its divisors is an integer number (7093622).

Almost surely, 2^21280863 is an apocalyptic number.

21280863 is a deficient number, since it is larger than the sum of its proper divisors (7093625).

21280863 is an equidigital number, since it uses as much as digits as its factorization.

21280863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7093624.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 21280863 is about 4613.1185764079. The cubic root of 21280863 is about 277.1169424599.

The spelling of 21280863 in words is "twenty-one million, two hundred eighty thousand, eight hundred sixty-three".