16851121561 has 2 divisors, whose sum is σ = 16851121562. Its totient is φ = 16851121560.

The previous prime is 16851121543. The next prime is 16851121579. The reversal of 16851121561 is 16512115861.

It is a balanced prime because it is at equal distance from previous prime (16851121543) and next prime (16851121579).

It can be written as a sum of positive squares in only one way, i.e., 12876575625 + 3974545936 = 113475^2 + 63044^2 .

It is a cyclic number.

It is not a de Polignac number, because 16851121561 - 2¹⁷ = 16850990489 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 16851121561.

It is not a weakly prime, because it can be changed into another prime (16851121501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8425560780 + 8425560781.

It is an arithmetic number, because the mean of its divisors is an integer number (8425560781).

Almost surely, 2^16851121561 is an apocalyptic number.

It is an amenable number.

16851121561 is a deficient number, since it is larger than the sum of its proper divisors (1).

16851121561 is an equidigital number, since it uses as much as digits as its factorization.

16851121561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14400, while the sum is 37.

The spelling of 16851121561 in words is "sixteen billion, eight hundred fifty-one million, one hundred twenty-one thousand, five hundred sixty-one".