21550565 has 8 divisors (see below), whose sum is σ = 25890840. Its totient is φ = 17220352.

The previous prime is 21550561. The next prime is 21550589. The reversal of 21550565 is 56505512.

It can be written as a sum of positive squares in 4 ways, for example, as 2401 + 21548164 = 49^2 + 4642^2 .

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 21550565 - 2² = 21550561 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21550561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3521 + ... + 7449.

It is an arithmetic number, because the mean of its divisors is an integer number (3236355).

Almost surely, 2^21550565 is an apocalyptic number.

It is an amenable number.

21550565 is a deficient number, since it is larger than the sum of its proper divisors (4340275).

21550565 is a wasteful number, since it uses less digits than its factorization.

21550565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5031.

The product of its (nonzero) digits is 7500, while the sum is 29.

The square root of 21550565 is about 4642.2586097718. The cubic root of 21550565 is about 278.2827075942.

The spelling of 21550565 in words is "twenty-one million, five hundred fifty thousand, five hundred sixty-five".