21344643 has 6 divisors (see below), whose sum is σ = 30831164. Its totient is φ = 14229756.

The previous prime is 21344629. The next prime is 21344663. The reversal of 21344643 is 34644312.

21344643 is a `hidden beast` number, since 2 + 13 + 4 + 4 + 643 = 666.

It is not a de Polignac number, because 21344643 - 2⁹ = 21344131 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21344623) 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 5 ways as a sum of consecutive naturals, for example, 1185805 + ... + 1185822.

Almost surely, 2^21344643 is an apocalyptic number.

21344643 is a deficient number, since it is larger than the sum of its proper divisors (9486521).

21344643 is a wasteful number, since it uses less digits than its factorization.

21344643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2371633 (or 2371630 counting only the distinct ones).

The product of its digits is 6912, while the sum is 27.

The square root of 21344643 is about 4620.0262986264. The cubic root of 21344643 is about 277.3935116126.

Adding to 21344643 its reverse (34644312), we get a palindrome (55988955).

The spelling of 21344643 in words is "twenty-one million, three hundred forty-four thousand, six hundred forty-three".