16561999939 has 2 divisors, whose sum is σ = 16561999940. Its totient is φ = 16561999938.

The previous prime is 16561999931. The next prime is 16561999997. The reversal of 16561999939 is 93999916561.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 16561999939 - 2³ = 16561999931 is a prime.

It is not a weakly prime, because it can be changed into another prime (16561999931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8280999969 + 8280999970.

It is an arithmetic number, because the mean of its divisors is an integer number (8280999970).

Almost surely, 2^16561999939 is an apocalyptic number.

16561999939 is a deficient number, since it is larger than the sum of its proper divisors (1).

16561999939 is an equidigital number, since it uses as much as digits as its factorization.

16561999939 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31886460, while the sum is 67.

The spelling of 16561999939 in words is "sixteen billion, five hundred sixty-one million, nine hundred ninety-nine thousand, nine hundred thirty-nine".