21687585 has 16 divisors (see below), whose sum is σ = 34819200. Its totient is φ = 11527040.

The previous prime is 21687583. The next prime is 21687593. The reversal of 21687585 is 58578612.

It is not a de Polignac number, because 21687585 - 2¹ = 21687583 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21687581) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2341 + ... + 6989.

It is an arithmetic number, because the mean of its divisors is an integer number (2176200).

Almost surely, 2^21687585 is an apocalyptic number.

It is an amenable number.

21687585 is a deficient number, since it is larger than the sum of its proper divisors (13131615).

21687585 is a wasteful number, since it uses less digits than its factorization.

21687585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4968.

The product of its digits is 134400, while the sum is 42.

The square root of 21687585 is about 4656.9931286185. The cubic root of 21687585 is about 278.8712423440.

The spelling of 21687585 in words is "twenty-one million, six hundred eighty-seven thousand, five hundred eighty-five".