16815691549 has 2 divisors, whose sum is σ = 16815691550. Its totient is φ = 16815691548.

The previous prime is 16815691511. The next prime is 16815691567. The reversal of 16815691549 is 94519651861.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16584803524 + 230888025 = 128782^2 + 15195^2 .

It is a cyclic number.

It is not a de Polignac number, because 16815691549 - 2¹⁵ = 16815658781 is a prime.

It is a super-2 number, since 2×16815691549² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 16815691549.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16815691649) 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, 8407845774 + 8407845775.

It is an arithmetic number, because the mean of its divisors is an integer number (8407845775).

Almost surely, 2^16815691549 is an apocalyptic number.

It is an amenable number.

16815691549 is a deficient number, since it is larger than the sum of its proper divisors (1).

16815691549 is an equidigital number, since it uses as much as digits as its factorization.

16815691549 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2332800, while the sum is 55.

The spelling of 16815691549 in words is "sixteen billion, eight hundred fifteen million, six hundred ninety-one thousand, five hundred forty-nine".