21421585 has 4 divisors (see below), whose sum is σ = 25705908. Its totient is φ = 17137264.

The previous prime is 21421559. The next prime is 21421597. The reversal of 21421585 is 58512412.

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 5803281 + 15618304 = 2409^2 + 3952^2 .

It is a cyclic number.

It is not a de Polignac number, because 21421585 - 2¹³ = 21413393 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2142154 + ... + 2142163.

It is an arithmetic number, because the mean of its divisors is an integer number (6426477).

Almost surely, 2^21421585 is an apocalyptic number.

It is an amenable number.

21421585 is a deficient number, since it is larger than the sum of its proper divisors (4284323).

21421585 is an equidigital number, since it uses as much as digits as its factorization.

21421585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4284322.

The product of its digits is 3200, while the sum is 28.

The square root of 21421585 is about 4628.3458168119. The cubic root of 21421585 is about 277.7264228914.

Adding to 21421585 its reverse (58512412), we get a palindrome (79933997).

The spelling of 21421585 in words is "twenty-one million, four hundred twenty-one thousand, five hundred eighty-five".