21553385 has 12 divisors (see below), whose sum is σ = 30087108. Its totient is φ = 14779296.

The previous prime is 21553379. The next prime is 21553393. The reversal of 21553385 is 58335512.

It can be written as a sum of positive squares in 2 ways, for example, as 4380649 + 17172736 = 2093^2 + 4144^2 .

It is not a de Polignac number, because 21553385 - 2¹² = 21549289 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 43742 + ... + 44231.

It is an arithmetic number, because the mean of its divisors is an integer number (2507259).

Almost surely, 2^21553385 is an apocalyptic number.

It is an amenable number.

21553385 is a deficient number, since it is larger than the sum of its proper divisors (8533723).

21553385 is an equidigital number, since it uses as much as digits as its factorization.

21553385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87992 (or 87985 counting only the distinct ones).

The product of its digits is 18000, while the sum is 32.

The square root of 21553385 is about 4642.5623312994. The cubic root of 21553385 is about 278.2948452962.

Adding to 21553385 its reverse (58335512), we get a palindrome (79888897).

The spelling of 21553385 in words is "twenty-one million, five hundred fifty-three thousand, three hundred eighty-five".