169981 has 6 divisors (see below), whose sum is σ = 197790. Its totient is φ = 145656.

The previous prime is 169957. The next prime is 169987. The reversal of 169981 is 189961.

It can be written as a sum of positive squares in only one way, i.e., 99225 + 70756 = 315^2 + 266^2 .

It is a de Polignac number, because none of the positive numbers 2^k-169981 is a prime.

It is a super-2 number, since 2×169981² = 57787080722, which contains 22 as substring.

It is a Duffinian number.

169981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (169987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1686 + ... + 1783.

It is an arithmetic number, because the mean of its divisors is an integer number (32965).

2¹⁶⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

169981 is a deficient number, since it is larger than the sum of its proper divisors (27809).

169981 is an equidigital number, since it uses as much as digits as its factorization.

169981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3483 (or 3476 counting only the distinct ones).

The product of its digits is 3888, while the sum is 34.

The square root of 169981 is about 412.2875210336. The cubic root of 169981 is about 55.3945186964.

The spelling of 169981 in words is "one hundred sixty-nine thousand, nine hundred eighty-one".