21061585 has 4 divisors (see below), whose sum is σ = 25273908. Its totient is φ = 16849264.

The previous prime is 21061541. The next prime is 21061591. The reversal of 21061585 is 58516012.

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 5157441 + 15904144 = 2271^2 + 3988^2 .

It is a cyclic number.

It is not a de Polignac number, because 21061585 - 2¹¹ = 21059537 is a prime.

It is a super-3 number, since 3×21061585³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is an unprimeable number.

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, 2106154 + ... + 2106163.

It is an arithmetic number, because the mean of its divisors is an integer number (6318477).

Almost surely, 2^21061585 is an apocalyptic number.

It is an amenable number.

21061585 is a deficient number, since it is larger than the sum of its proper divisors (4212323).

21061585 is an equidigital number, since it uses as much as digits as its factorization.

21061585 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4212322.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 21061585 is about 4589.2902501367. The cubic root of 21061585 is about 276.1618502148.

Adding to 21061585 its reverse (58516012), we get a palindrome (79577597).

The spelling of 21061585 in words is "twenty-one million, sixty-one thousand, five hundred eighty-five".