21158587 has 4 divisors (see below), whose sum is σ = 21174880. Its totient is φ = 21142296.

The previous prime is 21158563. The next prime is 21158633. The reversal of 21158587 is 78585112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21158587 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21158987) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6012 + ... + 8857.

It is an arithmetic number, because the mean of its divisors is an integer number (5293720).

Almost surely, 2^21158587 is an apocalyptic number.

21158587 is a deficient number, since it is larger than the sum of its proper divisors (16293).

21158587 is a wasteful number, since it uses less digits than its factorization.

21158587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16292.

The product of its digits is 22400, while the sum is 37.

The square root of 21158587 is about 4599.8464104794. The cubic root of 21158587 is about 276.5851680080.

The spelling of 21158587 in words is "twenty-one million, one hundred fifty-eight thousand, five hundred eighty-seven".