• 404 can be written using four 4's:

404 has 6 divisors (see below), whose sum is σ = 714. Its totient is φ = 200.

The previous prime is 401. The next prime is 409.

It is a happy number.

404 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in only one way, i.e., 400 + 4 = 20^2 + 2^2 .

404 is an undulating number in base 10.

It is a plaindrome in base 3, base 7, base 9, base 11 and base 15.

It is a zygodrome in base 3.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 391 and 400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 47 + ... + 54.

It is an arithmetic number, because the mean of its divisors is an integer number (119).

It is an amenable number.

404 is a deficient number, since it is larger than the sum of its proper divisors (310).

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

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

The sum of its prime factors is 105 (or 103 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 8.

The square root of 404 is about 20.0997512422. The cubic root of 404 is about 7.3925417917.

It can be divided in two parts, 40 and 4, that added together give a palindrome (44).

The spelling of 404 in words is "four hundred four", and thus it is an aban number and an iban number.

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