16781215664449 has 2 divisors, whose sum is σ = 16781215664450. Its totient is φ = 16781215664448.

The previous prime is 16781215664407. The next prime is 16781215664467. The reversal of 16781215664449 is 94446651218761.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13548789233424 + 3232426431025 = 3680868^2 + 1797895^2 .

It is a cyclic number.

It is not a de Polignac number, because 16781215664449 - 2⁷ = 16781215664321 is a prime.

It is a super-3 number, since 3×16781215664449³ (a number of 41 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (16781215664749) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8390607832224 + 8390607832225.

It is an arithmetic number, because the mean of its divisors is an integer number (8390607832225).

Almost surely, 2^{16781215664449} is an apocalyptic number.

It is an amenable number.

16781215664449 is a deficient number, since it is larger than the sum of its proper divisors (1).

16781215664449 is an equidigital number, since it uses as much as digits as its factorization.

16781215664449 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69672960, while the sum is 64.

The spelling of 16781215664449 in words is "sixteen trillion, seven hundred eighty-one billion, two hundred fifteen million, six hundred sixty-four thousand, four hundred forty-nine".