21654817 has 4 divisors (see below), whose sum is σ = 22009876. Its totient is φ = 21299760.

The previous prime is 21654811. The next prime is 21654839. The reversal of 21654817 is 71845612.

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 1079521 + 20575296 = 1039^2 + 4536^2 .

It is a cyclic number.

It is not a de Polignac number, because 21654817 - 2¹¹ = 21652769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21654811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 177438 + ... + 177559.

It is an arithmetic number, because the mean of its divisors is an integer number (5502469).

Almost surely, 2^21654817 is an apocalyptic number.

It is an amenable number.

21654817 is a deficient number, since it is larger than the sum of its proper divisors (355059).

21654817 is an equidigital number, since it uses as much as digits as its factorization.

21654817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 355058.

The product of its digits is 13440, while the sum is 34.

The square root of 21654817 is about 4653.4736487918. The cubic root of 21654817 is about 278.7307217190.

The spelling of 21654817 in words is "twenty-one million, six hundred fifty-four thousand, eight hundred seventeen".