161778640 has 20 divisors (see below), whose sum is σ = 376135524. Its totient is φ = 64711424.

The previous prime is 161778611. The next prime is 161778667. The reversal of 161778640 is 46877161.

It can be written as a sum of positive squares in 2 ways, for example, as 106007616 + 55771024 = 10296^2 + 7468^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 161778593 and 161778602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1011037 + ... + 1011196.

Almost surely, 2^161778640 is an apocalyptic number.

161778640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161778640 is an abundant number, since it is smaller than the sum of its proper divisors (214356884).

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

161778640 is a wasteful number, since it uses less digits than its factorization.

161778640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2022246 (or 2022240 counting only the distinct ones).

The product of its (nonzero) digits is 56448, while the sum is 40.

The square root of 161778640 is about 12719.2232467238. The cubic root of 161778640 is about 544.8877697248.

The spelling of 161778640 in words is "one hundred sixty-one million, seven hundred seventy-eight thousand, six hundred forty".