16781215664491 has 2 divisors, whose sum is σ = 16781215664492. Its totient is φ = 16781215664490.

The previous prime is 16781215664467. The next prime is 16781215664513. The reversal of 16781215664491 is 19446651218761.

It is a happy number.

16781215664491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 16781215664491 - 2¹⁷ = 16781215533419 is a prime.

It is a super-2 number, since 2×16781215664491² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (16781215664401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8390607832245 + 8390607832246.

It is an arithmetic number, because the mean of its divisors is an integer number (8390607832246).

Almost surely, 2^{16781215664491} is an apocalyptic number.

16781215664491 is a deficient number, since it is larger than the sum of its proper divisors (1).

16781215664491 is an equidigital number, since it uses as much as digits as its factorization.

16781215664491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17418240, while the sum is 61.

The spelling of 16781215664491 in words is "sixteen trillion, seven hundred eighty-one billion, two hundred fifteen million, six hundred sixty-four thousand, four hundred ninety-one".