16642664561 has 2 divisors, whose sum is σ = 16642664562. Its totient is φ = 16642664560.

The previous prime is 16642664531. The next prime is 16642664627. The reversal of 16642664561 is 16546624661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12120909025 + 4521755536 = 110095^2 + 67244^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16642664561 is a prime.

It is not a weakly prime, because it can be changed into another prime (16642664531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8321332280 + 8321332281.

It is an arithmetic number, because the mean of its divisors is an integer number (8321332281).

Almost surely, 2^16642664561 is an apocalyptic number.

It is an amenable number.

16642664561 is a deficient number, since it is larger than the sum of its proper divisors (1).

16642664561 is an equidigital number, since it uses as much as digits as its factorization.

16642664561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1244160, while the sum is 47.

The spelling of 16642664561 in words is "sixteen billion, six hundred forty-two million, six hundred sixty-four thousand, five hundred sixty-one".