21280385 has 8 divisors (see below), whose sum is σ = 29184576. Its totient is φ = 14592240.

The previous prime is 21280381. The next prime is 21280387. The reversal of 21280385 is 58308212.

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

It is not a de Polignac number, because 21280385 - 2² = 21280381 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21280381) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 303971 + ... + 304040.

It is an arithmetic number, because the mean of its divisors is an integer number (3648072).

Almost surely, 2^21280385 is an apocalyptic number.

It is an amenable number.

21280385 is a deficient number, since it is larger than the sum of its proper divisors (7904191).

21280385 is an equidigital number, since it uses as much as digits as its factorization.

21280385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 608023.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 21280385 is about 4613.0667673469. The cubic root of 21280385 is about 277.1148676241.

Adding to 21280385 its reverse (58308212), we get a palindrome (79588597).

The spelling of 21280385 in words is "twenty-one million, two hundred eighty thousand, three hundred eighty-five".