21618587 has 4 divisors (see below), whose sum is σ = 21892320. Its totient is φ = 21344856.

The previous prime is 21618581. The next prime is 21618593. The reversal of 21618587 is 78581612.

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

It is an interprime number because it is at equal distance from previous prime (21618581) and next prime (21618593).

It is a cyclic number.

It is not a de Polignac number, because 21618587 - 2¹² = 21614491 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21618587.

It is not an unprimeable number, because it can be changed into a prime (21618581) 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, 136748 + ... + 136905.

It is an arithmetic number, because the mean of its divisors is an integer number (5473080).

Almost surely, 2^21618587 is an apocalyptic number.

21618587 is a deficient number, since it is larger than the sum of its proper divisors (273733).

21618587 is an equidigital number, since it uses as much as digits as its factorization.

21618587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273732.

The product of its digits is 26880, while the sum is 38.

The square root of 21618587 is about 4649.5792282743. The cubic root of 21618587 is about 278.5751897179.

The spelling of 21618587 in words is "twenty-one million, six hundred eighteen thousand, five hundred eighty-seven".