161638 has 4 divisors (see below), whose sum is σ = 242460. Its totient is φ = 80818.

The previous prime is 161627. The next prime is 161639. The reversal of 161638 is 836161.

It is a semiprime because it is the product of two primes.

It is a super-2 number, since 2×161638² = 52253686088, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161639) 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 as a sum of consecutive naturals, namely, 40408 + ... + 40411.

It is an arithmetic number, because the mean of its divisors is an integer number (60615).

2¹⁶¹⁶³⁸ is an apocalyptic number.

161638 is a deficient number, since it is larger than the sum of its proper divisors (80822).

161638 is an equidigital number, since it uses as much as digits as its factorization.

161638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80821.

The product of its digits is 864, while the sum is 25.

The square root of 161638 is about 402.0422863332. The cubic root of 161638 is about 54.4729827091.

Adding to 161638 its reverse (836161), we get a palindrome (997799).

The spelling of 161638 in words is "one hundred sixty-one thousand, six hundred thirty-eight".