21818641 has 8 divisors (see below), whose sum is σ = 24132584. Its totient is φ = 19595520.

The previous prime is 21818627. The next prime is 21818647. The reversal of 21818641 is 14681812.

It can be written as a sum of positive squares in 4 ways, for example, as 103041 + 21715600 = 321^2 + 4660^2 .

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 21818641 - 2⁵ = 21818609 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21818647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22200 + ... + 23161.

It is an arithmetic number, because the mean of its divisors is an integer number (3016573).

Almost surely, 2^21818641 is an apocalyptic number.

It is an amenable number.

21818641 is a deficient number, since it is larger than the sum of its proper divisors (2313943).

21818641 is a wasteful number, since it uses less digits than its factorization.

21818641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45411.

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

The square root of 21818641 is about 4671.0428171876. The cubic root of 21818641 is about 279.4318453727.

The spelling of 21818641 in words is "twenty-one million, eight hundred eighteen thousand, six hundred forty-one".