21521585 has 16 divisors (see below), whose sum is σ = 27466560. Its totient is φ = 16142400.

The previous prime is 21521579. The next prime is 21521587. The reversal of 21521585 is 58512512.

It is not a de Polignac number, because 21521585 - 2⁸ = 21521329 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21521587) 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, 8474 + ... + 10716.

It is an arithmetic number, because the mean of its divisors is an integer number (1716660).

Almost surely, 2^21521585 is an apocalyptic number.

It is an amenable number.

21521585 is a deficient number, since it is larger than the sum of its proper divisors (5944975).

21521585 is a wasteful number, since it uses less digits than its factorization.

21521585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2368.

The product of its digits is 4000, while the sum is 29.

The square root of 21521585 is about 4639.1362342574. The cubic root of 21521585 is about 278.1579119408.

The spelling of 21521585 in words is "twenty-one million, five hundred twenty-one thousand, five hundred eighty-five".