161778665 has 8 divisors (see below), whose sum is σ = 202575168. Its totient is φ = 123795760.

The previous prime is 161778611. The next prime is 161778667. The reversal of 161778665 is 566877161.

161778665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 161778665 - 2²⁶ = 94669801 is a prime.

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, 703271 + ... + 703500.

It is an arithmetic number, because the mean of its divisors is an integer number (25321896).

Almost surely, 2^161778665 is an apocalyptic number.

It is an amenable number.

161778665 is a deficient number, since it is larger than the sum of its proper divisors (40796503).

161778665 is a wasteful number, since it uses less digits than its factorization.

161778665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1406799.

The product of its digits is 423360, while the sum is 47.

The square root of 161778665 is about 12719.2242294882. The cubic root of 161778665 is about 544.8877977924.

It can be divided in two parts, 16177 and 8665, that added together give a palindrome (24842).

The spelling of 161778665 in words is "one hundred sixty-one million, seven hundred seventy-eight thousand, six hundred sixty-five".