• 169 can be written using four 4's:

See also 113.

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169 has 3 divisors (see below), whose sum is σ = 183. Its totient is φ = 156.

The previous prime is 167. The next prime is 173. The reversal of 169 is 961.

169 = T₁₂ + T₁₃.

The square root of 169 is 13.

It is a perfect power (a square), and thus also a powerful number.

169 is nontrivially palindromic in base 12.

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

169 is an esthetic number in base 12 and base 16, because in such bases its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 961 = 31².

It can be written as a sum of positive squares in only one way, i.e., 25 + 144 = 5^2 + 12^2 .

It is not a de Polignac number, because 169 - 2¹ = 167 is a prime.

It is a super-2 number, since 2×169² = 57122, which contains 22 as substring.

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

It is a Duffinian number.

169 is an undulating number in base 12.

169 is a lucky number.

It is a plaindrome in base 5, base 10 and base 11.

It is a nialpdrome in base 4, base 6, base 7, base 13, base 14, base 15 and base 16.

It is a panconsummate number.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 7 + ... + 19.

It is an arithmetic number, because the mean of its divisors is an integer number (61).

169 is the 13-th square number.

169 is the 8-th hex number and also the 7-th centered octagonal number.

It is an amenable number.

169 is a deficient number, since it is larger than the sum of its proper divisors (14).

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

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

The sum of its prime factors is 26 (or 13 counting only the distinct ones).

The product of its digits is 54, while the sum is 16.

The cubic root of 169 is about 5.5287748137.

Subtracting from 169 its sum of digits (16), we obtain a triangular number (153 = T₁₇).

Multiplying 169 by its sum of digits (16), we get a square (2704 = 52²).

Multiplying 169 by its reverse (961), we get a square (162409 = 403²).

It can be divided in two parts, 16 and 9, that multiplied together give a square (144 = 12²).

The spelling of 169 in words is "one hundred sixty-nine", and thus it is an aban number.