16781215664399 has 16 divisors (see below), whose sum is σ = 16971193843200. Its totient is φ = 16592561669376.

The previous prime is 16781215664351. The next prime is 16781215664401. The reversal of 16781215664399 is 99346651218761.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16781215664399 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16781215664299) 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, 23096447 + ... + 23811935.

It is an arithmetic number, because the mean of its divisors is an integer number (1060699615200).

Almost surely, 2^{16781215664399} is an apocalyptic number.

16781215664399 is a deficient number, since it is larger than the sum of its proper divisors (189978178801).

16781215664399 is a wasteful number, since it uses less digits than its factorization.

16781215664399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 716414.

The product of its digits is 117573120, while the sum is 68.

The spelling of 16781215664399 in words is "sixteen trillion, seven hundred eighty-one billion, two hundred fifteen million, six hundred sixty-four thousand, three hundred ninety-nine".