21618841 has 8 divisors (see below), whose sum is σ = 22264200. Its totient is φ = 20976768.

The previous prime is 21618803. The next prime is 21618847. The reversal of 21618841 is 14881612.

It can be written as a sum of positive squares in 4 ways, for example, as 7209225 + 14409616 = 2685^2 + 3796^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21618841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21618847) 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, 20085 + ... + 21133.

It is an arithmetic number, because the mean of its divisors is an integer number (2783025).

Almost surely, 2^21618841 is an apocalyptic number.

It is an amenable number.

21618841 is a deficient number, since it is larger than the sum of its proper divisors (645359).

21618841 is a wasteful number, since it uses less digits than its factorization.

21618841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1643.

The product of its digits is 3072, while the sum is 31.

The square root of 21618841 is about 4649.6065424937. The cubic root of 21618841 is about 278.5762807207.

The spelling of 21618841 in words is "twenty-one million, six hundred eighteen thousand, eight hundred forty-one".