21317643 has 24 divisors (see below), whose sum is σ = 32786208. Its totient is φ = 13300992.

The previous prime is 21317627. The next prime is 21317651. The reversal of 21317643 is 34671312.

21317643 is a `hidden beast` number, since 2 + 1 + 3 + 17 + 643 = 666.

It is not a de Polignac number, because 21317643 - 2⁴ = 21317627 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21317623) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 42130 + ... + 42632.

It is an arithmetic number, because the mean of its divisors is an integer number (1366092).

Almost surely, 2^21317643 is an apocalyptic number.

21317643 is a deficient number, since it is larger than the sum of its proper divisors (11468565).

21317643 is a wasteful number, since it uses less digits than its factorization.

21317643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 803 (or 800 counting only the distinct ones).

The product of its digits is 3024, while the sum is 27.

The square root of 21317643 is about 4617.1033126843. The cubic root of 21317643 is about 277.2764988794.

Adding to 21317643 its reverse (34671312), we get a palindrome (55988955).

The spelling of 21317643 in words is "twenty-one million, three hundred seventeen thousand, six hundred forty-three".