21138587 has 8 divisors (see below), whose sum is σ = 22274304. Its totient is φ = 20020968.

The previous prime is 21138577. The next prime is 21138589. The reversal of 21138587 is 78583112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21138587 - 2¹⁰ = 21137563 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21138589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2093 + ... + 6830.

It is an arithmetic number, because the mean of its divisors is an integer number (2784288).

Almost surely, 2^21138587 is an apocalyptic number.

21138587 is a deficient number, since it is larger than the sum of its proper divisors (1135717).

21138587 is a wasteful number, since it uses less digits than its factorization.

21138587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9049.

The product of its digits is 13440, while the sum is 35.

The square root of 21138587 is about 4597.6719108697. The cubic root of 21138587 is about 276.4979938313.

The spelling of 21138587 in words is "twenty-one million, one hundred thirty-eight thousand, five hundred eighty-seven".