21938566 has 24 divisors (see below), whose sum is σ = 36418464. Its totient is φ = 9902880.

The previous prime is 21938563. The next prime is 21938569. The reversal of 21938566 is 66583912.

It is an interprime number because it is at equal distance from previous prime (21938563) and next prime (21938569).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21938563) 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 11 ways as a sum of consecutive naturals, for example, 15196 + ... + 16576.

It is an arithmetic number, because the mean of its divisors is an integer number (1517436).

Almost surely, 2^21938566 is an apocalyptic number.

21938566 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21938566 is a deficient number, since it is larger than the sum of its proper divisors (14479898).

21938566 is a wasteful number, since it uses less digits than its factorization.

21938566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1456 (or 1443 counting only the distinct ones).

The product of its digits is 77760, while the sum is 40.

The square root of 21938566 is about 4683.8622951577. The cubic root of 21938566 is about 279.9428709977.

The spelling of 21938566 in words is "twenty-one million, nine hundred thirty-eight thousand, five hundred sixty-six".