21660556661727 has 16 divisors (see below), whose sum is σ = 29207210778720. Its totient is φ = 14277158669312.

The previous prime is 21660556661693. The next prime is 21660556661749. The reversal of 21660556661727 is 72716665506612.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21660556661727 - 2¹⁶ = 21660556596191 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21660556661027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1254613 + ... + 6700385.

It is an arithmetic number, because the mean of its divisors is an integer number (1825450673670).

Almost surely, 2^{21660556661727} is an apocalyptic number.

21660556661727 is a deficient number, since it is larger than the sum of its proper divisors (7546654116993).

21660556661727 is a wasteful number, since it uses less digits than its factorization.

21660556661727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5460762.

The product of its (nonzero) digits is 38102400, while the sum is 60.

The spelling of 21660556661727 in words is "twenty-one trillion, six hundred sixty billion, five hundred fifty-six million, six hundred sixty-one thousand, seven hundred twenty-seven".