21668428804 has 27 divisors (see below), whose sum is σ = 41686617063. Its totient is φ = 9847813800.

The previous prime is 21668428801. The next prime is 21668428891. The reversal of 21668428804 is 40882486612.

The square root of 21668428804 is 147202.

It is a perfect power (a square), and thus also a powerful number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21668428801) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3235099 + ... + 3241789.

Almost surely, 2^21668428804 is an apocalyptic number.

21668428804 is the 147202-nd square number.

It is an amenable number.

21668428804 is a deficient number, since it is larger than the sum of its proper divisors (20018188259).

21668428804 is an frugal number, since it uses more digits than its factorization.

21668428804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13408 (or 6704 counting only the distinct ones).

The product of its (nonzero) digits is 1179648, while the sum is 49.

Multiplying 21668428804 by its sum of digits (49), we get a square (1061753011396 = 1030414²).

The spelling of 21668428804 in words is "twenty-one billion, six hundred sixty-eight million, four hundred twenty-eight thousand, eight hundred four".