161778666 has 16 divisors (see below), whose sum is σ = 369779904. Its totient is φ = 46222464.

The previous prime is 161778611. The next prime is 161778667. The reversal of 161778666 is 666877161.

161778666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (161778667) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1925895 + ... + 1925978.

It is an arithmetic number, because the mean of its divisors is an integer number (23111244).

Almost surely, 2^161778666 is an apocalyptic number.

161778666 is an abundant number, since it is smaller than the sum of its proper divisors (208001238).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

161778666 is a wasteful number, since it uses less digits than its factorization.

161778666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3851885.

The product of its digits is 508032, while the sum is 48.

The square root of 161778666 is about 12719.2242687988. The cubic root of 161778666 is about 544.8877989151.

The spelling of 161778666 in words is "one hundred sixty-one million, seven hundred seventy-eight thousand, six hundred sixty-six".