21641617 has 4 divisors (see below), whose sum is σ = 21663040. Its totient is φ = 21620196.

The previous prime is 21641611. The next prime is 21641671. The reversal of 21641617 is 71614612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21641617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21641611) 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, 9117 + ... + 11242.

It is an arithmetic number, because the mean of its divisors is an integer number (5415760).

Almost surely, 2^21641617 is an apocalyptic number.

It is an amenable number.

21641617 is a deficient number, since it is larger than the sum of its proper divisors (21423).

21641617 is a wasteful number, since it uses less digits than its factorization.

21641617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21422.

The product of its digits is 2016, while the sum is 28.

The square root of 21641617 is about 4652.0551372485. The cubic root of 21641617 is about 278.6740754563.

The spelling of 21641617 in words is "twenty-one million, six hundred forty-one thousand, six hundred seventeen".