21668164556 has 24 divisors (see below), whose sum is σ = 38925337920. Its totient is φ = 10550397312.

The previous prime is 21668164541. The next prime is 21668164603. The reversal of 21668164556 is 65546186612.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 446591 + ... + 492726.

It is an arithmetic number, because the mean of its divisors is an integer number (1621889080).

Almost surely, 2^21668164556 is an apocalyptic number.

It is an amenable number.

21668164556 is a deficient number, since it is larger than the sum of its proper divisors (17257173364).

21668164556 is a wasteful number, since it uses less digits than its factorization.

21668164556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 939473 (or 939471 counting only the distinct ones).

The product of its digits is 2073600, while the sum is 50.

The spelling of 21668164556 in words is "twenty-one billion, six hundred sixty-eight million, one hundred sixty-four thousand, five hundred fifty-six".