161778557 has 2 divisors, whose sum is σ = 161778558. Its totient is φ = 161778556.

The previous prime is 161778503. The next prime is 161778611. The reversal of 161778557 is 755877161.

It is a balanced prime because it is at equal distance from previous prime (161778503) and next prime (161778611).

It can be written as a sum of positive squares in only one way, i.e., 129640996 + 32137561 = 11386^2 + 5669^2 .

It is a cyclic number.

It is not a de Polignac number, because 161778557 - 2⁶ = 161778493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161768557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80889278 + 80889279.

It is an arithmetic number, because the mean of its divisors is an integer number (80889279).

Almost surely, 2^161778557 is an apocalyptic number.

It is an amenable number.

161778557 is a deficient number, since it is larger than the sum of its proper divisors (1).

161778557 is an equidigital number, since it uses as much as digits as its factorization.

161778557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 411600, while the sum is 47.

The square root of 161778557 is about 12719.2199839456. The cubic root of 161778557 is about 544.8876765405.

The spelling of 161778557 in words is "one hundred sixty-one million, seven hundred seventy-eight thousand, five hundred fifty-seven".