21204003663 has 10 divisors (see below), whose sum is σ = 31675116704. Its totient is φ = 14136002388.

The previous prime is 21204003607. The next prime is 21204003749. The reversal of 21204003663 is 36630040212.

It is not a de Polignac number, because 21204003663 - 2²⁸ = 20935568207 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204003563) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 130888831 + ... + 130888992.

Almost surely, 2^21204003663 is an apocalyptic number.

21204003663 is a deficient number, since it is larger than the sum of its proper divisors (10471113041).

21204003663 is an equidigital number, since it uses as much as digits as its factorization.

21204003663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261777835 (or 261777826 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 27.

Adding to 21204003663 its reverse (36630040212), we get a palindrome (57834043875).

The spelling of 21204003663 in words is "twenty-one billion, two hundred four million, three thousand, six hundred sixty-three".