161778641 has 6 divisors (see below), whose sum is σ = 162803970. Its totient is φ = 160759728.

The previous prime is 161778611. The next prime is 161778667. The reversal of 161778641 is 146877161.

It can be written as a sum of positive squares in only one way, i.e., 119268241 + 42510400 = 10921^2 + 6520^2 .

It is not a de Polignac number, because 161778641 - 2¹⁰ = 161777617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161778611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 23525 + ... + 29613.

It is an arithmetic number, because the mean of its divisors is an integer number (27133995).

Almost surely, 2^161778641 is an apocalyptic number.

It is an amenable number.

161778641 is a deficient number, since it is larger than the sum of its proper divisors (1025329).

161778641 is an frugal number, since it uses more digits than its factorization.

161778641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6415 (or 6252 counting only the distinct ones).

The product of its digits is 56448, while the sum is 41.

The square root of 161778641 is about 12719.2232860344. The cubic root of 161778641 is about 544.8877708475.

The spelling of 161778641 in words is "one hundred sixty-one million, seven hundred seventy-eight thousand, six hundred forty-one".