21845617 has 4 divisors (see below), whose sum is σ = 21884580. Its totient is φ = 21806656.

The previous prime is 21845597. The next prime is 21845627. The reversal of 21845617 is 71654812.

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 5125696 + 16719921 = 2264^2 + 4089^2 .

It is a cyclic number.

It is not a de Polignac number, because 21845617 - 2⁷ = 21845489 is a prime.

It is a super-2 number, since 2×21845617² = 954461964221378, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21845627) 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 3 ways as a sum of consecutive naturals, for example, 18628 + ... + 19765.

It is an arithmetic number, because the mean of its divisors is an integer number (5471145).

Almost surely, 2^21845617 is an apocalyptic number.

It is an amenable number.

21845617 is a deficient number, since it is larger than the sum of its proper divisors (38963).

21845617 is an equidigital number, since it uses as much as digits as its factorization.

21845617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38962.

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

The square root of 21845617 is about 4673.9295031055. The cubic root of 21845617 is about 279.5469586989.

The spelling of 21845617 in words is "twenty-one million, eight hundred forty-five thousand, six hundred seventeen".