21345617 has 4 divisors (see below), whose sum is σ = 21552960. Its totient is φ = 21138276.

The previous prime is 21345593. The next prime is 21345619. The reversal of 21345617 is 71654312.

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 not a de Polignac number, because 21345617 - 2¹⁰ = 21344593 is a prime.

It is a super-2 number, since 2×21345617² = 911270730221378, which contains 22 as substring.

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 21345617.

It is not an unprimeable number, because it can be changed into a prime (21345619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 103517 + ... + 103722.

It is an arithmetic number, because the mean of its divisors is an integer number (5388240).

Almost surely, 2^21345617 is an apocalyptic number.

It is an amenable number.

21345617 is a deficient number, since it is larger than the sum of its proper divisors (207343).

21345617 is a wasteful number, since it uses less digits than its factorization.

21345617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 207342.

The product of its digits is 5040, while the sum is 29.

The square root of 21345617 is about 4620.1317080793. The cubic root of 21345617 is about 277.3977308940.

Adding to 21345617 its reverse (71654312), we get a palindrome (92999929).

The spelling of 21345617 in words is "twenty-one million, three hundred forty-five thousand, six hundred seventeen".