161691777 has 24 divisors (see below), whose sum is σ = 266319144. Its totient is φ = 93648384.

The previous prime is 161691713. The next prime is 161691781. The reversal of 161691777 is 777196161.

It can be written as a sum of positive squares in 4 ways, for example, as 3837681 + 157854096 = 1959^2 + 12564^2 .

It is not a de Polignac number, because 161691777 - 2⁶ = 161691713 is a prime.

It is a super-2 number, since 2×161691777² = 52288461498835458, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (161691707) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 38658 + ... + 42635.

It is an arithmetic number, because the mean of its divisors is an integer number (11096631).

Almost surely, 2^161691777 is an apocalyptic number.

161691777 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

It is an amenable number.

161691777 is a deficient number, since it is larger than the sum of its proper divisors (104627367).

161691777 is a wasteful number, since it uses less digits than its factorization.

161691777 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81329 (or 81326 counting only the distinct ones).

The product of its digits is 111132, while the sum is 45.

The square root of 161691777 is about 12715.8081536330. The cubic root of 161691777 is about 544.7902309730.

The spelling of 161691777 in words is "one hundred sixty-one million, six hundred ninety-one thousand, seven hundred seventy-seven".