21261841 has 4 divisors (see below), whose sum is σ = 21301684. Its totient is φ = 21222000.

The previous prime is 21261839. The next prime is 21261869. The reversal of 21261841 is 14816212.

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 7311616 + 13950225 = 2704^2 + 3735^2 .

It is a cyclic number.

It is not a de Polignac number, because 21261841 - 2¹ = 21261839 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21261811) 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, 19110 + ... + 20191.

It is an arithmetic number, because the mean of its divisors is an integer number (5325421).

Almost surely, 2^21261841 is an apocalyptic number.

It is an amenable number.

21261841 is a deficient number, since it is larger than the sum of its proper divisors (39843).

21261841 is an equidigital number, since it uses as much as digits as its factorization.

21261841 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39842.

The product of its digits is 768, while the sum is 25.

The square root of 21261841 is about 4611.0563865561. The cubic root of 21261841 is about 277.0343504169.

The spelling of 21261841 in words is "twenty-one million, two hundred sixty-one thousand, eight hundred forty-one".