21280865 has 8 divisors (see below), whose sum is σ = 26647488. Its totient is φ = 16284400.

The previous prime is 21280843. The next prime is 21280873. The reversal of 21280865 is 56808212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21280865 - 2¹⁶ = 21215329 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 92411 + ... + 92640.

It is an arithmetic number, because the mean of its divisors is an integer number (3330936).

Almost surely, 2^21280865 is an apocalyptic number.

It is an amenable number.

21280865 is a deficient number, since it is larger than the sum of its proper divisors (5366623).

21280865 is a wasteful number, since it uses less digits than its factorization.

21280865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185079.

The product of its (nonzero) digits is 7680, while the sum is 32.

The square root of 21280865 is about 4613.1187931810. The cubic root of 21280865 is about 277.1169511412.

The spelling of 21280865 in words is "twenty-one million, two hundred eighty thousand, eight hundred sixty-five".