21243263666 has 8 divisors (see below), whose sum is σ = 31866582384. Its totient is φ = 10621069540.

The previous prime is 21243263647. The next prime is 21243263669. The reversal of 21243263666 is 66636234212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21243263669) 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, 232220 + ... + 310503.

It is an arithmetic number, because the mean of its divisors is an integer number (3983322798).

Almost surely, 2^21243263666 is an apocalyptic number.

21243263666 is a deficient number, since it is larger than the sum of its proper divisors (10623318718).

21243263666 is a wasteful number, since it uses less digits than its factorization.

21243263666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 562296.

The product of its digits is 373248, while the sum is 41.

Adding to 21243263666 its reverse (66636234212), we get a palindrome (87879497878).

The spelling of 21243263666 in words is "twenty-one billion, two hundred forty-three million, two hundred sixty-three thousand, six hundred sixty-six".