21565241 has 8 divisors (see below), whose sum is σ = 22430280. Its totient is φ = 20708352.

The previous prime is 21565199. The next prime is 21565261. The reversal of 21565241 is 14256512.

It can be written as a sum of positive squares in 4 ways, for example, as 7155625 + 14409616 = 2675^2 + 3796^2 .

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 21565241 - 2⁶ = 21565177 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21565241.

It is not an unprimeable number, because it can be changed into a prime (21565261) 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, 3671 + ... + 7523.

It is an arithmetic number, because the mean of its divisors is an integer number (2803785).

Almost surely, 2^21565241 is an apocalyptic number.

It is an amenable number.

21565241 is a deficient number, since it is larger than the sum of its proper divisors (865039).

21565241 is a wasteful number, since it uses less digits than its factorization.

21565241 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4075.

The product of its digits is 2400, while the sum is 26.

The square root of 21565241 is about 4643.8390368315. The cubic root of 21565241 is about 278.3458637153.

It can be divided in two parts, 215 and 65241, that added together give a palindrome (65456).

The spelling of 21565241 in words is "twenty-one million, five hundred sixty-five thousand, two hundred forty-one".