21113643 has 32 divisors (see below), whose sum is σ = 31256064. Its totient is φ = 12621312.

The previous prime is 21113639. The next prime is 21113671. The reversal of 21113643 is 34631112.

It is not a de Polignac number, because 21113643 - 2² = 21113639 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21113633) 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 31 ways as a sum of consecutive naturals, for example, 126346 + ... + 126512.

It is an arithmetic number, because the mean of its divisors is an integer number (976752).

Almost surely, 2^21113643 is an apocalyptic number.

21113643 is a deficient number, since it is larger than the sum of its proper divisors (10142421).

21113643 is a wasteful number, since it uses less digits than its factorization.

21113643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291.

The product of its digits is 432, while the sum is 21.

The square root of 21113643 is about 4594.9584328914. The cubic root of 21113643 is about 276.3891931091.

Adding to 21113643 its reverse (34631112), we get a palindrome (55744755).

The spelling of 21113643 in words is "twenty-one million, one hundred thirteen thousand, six hundred forty-three".