21587641 has 4 divisors (see below), whose sum is σ = 21810292. Its totient is φ = 21364992.

The previous prime is 21587627. The next prime is 21587647. The reversal of 21587641 is 14678512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7868025 + 13719616 = 2805^2 + 3704^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21587641 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21587597 and 21587606.

It is not an unprimeable number, because it can be changed into a prime (21587647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111180 + ... + 111373.

It is an arithmetic number, because the mean of its divisors is an integer number (5452573).

Almost surely, 2^21587641 is an apocalyptic number.

It is an amenable number.

21587641 is a deficient number, since it is larger than the sum of its proper divisors (222651).

21587641 is an equidigital number, since it uses as much as digits as its factorization.

21587641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222650.

The product of its digits is 13440, while the sum is 34.

The square root of 21587641 is about 4646.2502085015. The cubic root of 21587641 is about 278.4422037752.

The spelling of 21587641 in words is "twenty-one million, five hundred eighty-seven thousand, six hundred forty-one".