16505335981 has 2 divisors, whose sum is σ = 16505335982. Its totient is φ = 16505335980.

The previous prime is 16505335943. The next prime is 16505336021. The reversal of 16505335981 is 18953350561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15692572900 + 812763081 = 125270^2 + 28509^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16505335981 is a prime.

It is a super-2 number, since 2×16505335981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16505335081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8252667990 + 8252667991.

It is an arithmetic number, because the mean of its divisors is an integer number (8252667991).

Almost surely, 2^16505335981 is an apocalyptic number.

It is an amenable number.

16505335981 is a deficient number, since it is larger than the sum of its proper divisors (1).

16505335981 is an equidigital number, since it uses as much as digits as its factorization.

16505335981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486000, while the sum is 46.

The spelling of 16505335981 in words is "sixteen billion, five hundred five million, three hundred thirty-five thousand, nine hundred eighty-one".