161687993 has 2 divisors, whose sum is σ = 161687994. Its totient is φ = 161687992.

The previous prime is 161687987. The next prime is 161688011. The reversal of 161687993 is 399786161.

161687993 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 115949824 + 45738169 = 10768^2 + 6763^2 .

It is a cyclic number.

It is not a de Polignac number, because 161687993 - 2⁸ = 161687737 is a prime.

It is a super-2 number, since 2×161687993² = 52286014160736098, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (161687693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80843996 + 80843997.

It is an arithmetic number, because the mean of its divisors is an integer number (80843997).

Almost surely, 2^161687993 is an apocalyptic number.

It is an amenable number.

161687993 is a deficient number, since it is larger than the sum of its proper divisors (1).

161687993 is an equidigital number, since it uses as much as digits as its factorization.

161687993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 489888, while the sum is 50.

The square root of 161687993 is about 12715.6593615903. The cubic root of 161687993 is about 544.7859811128.

The spelling of 161687993 in words is "one hundred sixty-one million, six hundred eighty-seven thousand, nine hundred ninety-three".