21455285 has 4 divisors (see below), whose sum is σ = 25746348. Its totient is φ = 17164224.

The previous prime is 21455281. The next prime is 21455293. The reversal of 21455285 is 58255412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 13010449 + 8444836 = 3607^2 + 2906^2 .

It is a cyclic number.

It is not a de Polignac number, because 21455285 - 2² = 21455281 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21455281) 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, 2145524 + ... + 2145533.

It is an arithmetic number, because the mean of its divisors is an integer number (6436587).

Almost surely, 2^21455285 is an apocalyptic number.

It is an amenable number.

21455285 is a deficient number, since it is larger than the sum of its proper divisors (4291063).

21455285 is an equidigital number, since it uses as much as digits as its factorization.

21455285 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4291062.

The product of its digits is 16000, while the sum is 32.

The square root of 21455285 is about 4631.9849956579. The cubic root of 21455285 is about 277.8719844320.

The spelling of 21455285 in words is "twenty-one million, four hundred fifty-five thousand, two hundred eighty-five".