21549841 has 4 divisors (see below), whose sum is σ = 21573684. Its totient is φ = 21526000.

The previous prime is 21549839. The next prime is 21549851. The reversal of 21549841 is 14894512.

It is a happy number.

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 18309841 + 3240000 = 4279^2 + 1800^2 .

It is a cyclic number.

It is not a de Polignac number, because 21549841 - 2¹ = 21549839 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21549797 and 21549806.

It is not an unprimeable number, because it can be changed into a prime (21549821) 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, 10510 + ... + 12391.

It is an arithmetic number, because the mean of its divisors is an integer number (5393421).

Almost surely, 2^21549841 is an apocalyptic number.

It is an amenable number.

21549841 is a deficient number, since it is larger than the sum of its proper divisors (23843).

21549841 is an equidigital number, since it uses as much as digits as its factorization.

21549841 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23842.

The product of its digits is 11520, while the sum is 34.

The square root of 21549841 is about 4642.1806298334. The cubic root of 21549841 is about 278.2795912191.

The spelling of 21549841 in words is "twenty-one million, five hundred forty-nine thousand, eight hundred forty-one".