16638556456681 has 4 divisors (see below), whose sum is σ = 16642688210512. Its totient is φ = 16634424702852.

The previous prime is 16638556456679. The next prime is 16638556456721. The reversal of 16638556456681 is 18665465583661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 16638556456681 - 2¹ = 16638556456679 is a prime.

It is a super-2 number, since 2×16638556456681² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16638556456681.

It is not an unprimeable number, because it can be changed into a prime (16638556456631) 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, 2065870875 + ... + 2065878928.

It is an arithmetic number, because the mean of its divisors is an integer number (4160672052628).

Almost surely, 2^{16638556456681} is an apocalyptic number.

It is an amenable number.

16638556456681 is a deficient number, since it is larger than the sum of its proper divisors (4131753831).

16638556456681 is an equidigital number, since it uses as much as digits as its factorization.

16638556456681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4131753830.

The product of its digits is 746496000, while the sum is 70.

The spelling of 16638556456681 in words is "sixteen trillion, six hundred thirty-eight billion, five hundred fifty-six million, four hundred fifty-six thousand, six hundred eighty-one".