• 660 can be written using four 4's:

• 660 can be written using four 4's:

660 has 24 divisors (see below), whose sum is σ = 2016. Its totient is φ = 160.

The previous prime is 659. The next prime is 661. The reversal of 660 is 66.

660 = T_{5} + T_{6} + ... +
T_{15}.

660 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (659) and next prime (661).

It is a hoax number, since the sum of its digits (12) coincides with the sum of the digits of its distinct prime factors.

660 is a Gilda number.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a O'Halloran number.

It is a plaindrome in base 8.

It is a nialpdrome in base 4, base 10 and base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55 + ... + 65.

It is an arithmetic number, because the mean of its divisors is an integer number (84).

2^{660} is an apocalyptic number.

660 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1008).

660 is an abundant number, since it is smaller than the sum of its proper divisors (1356).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

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

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

The sum of its prime factors is 23 (or 21 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 12.

The square root of 660 is about 25.6904651573. The cubic root of 660 is about 8.7065876912.

660 divided by its sum of digits (12) gives a palindrome (55).

Adding to 660 its product of nonzero digits (36), we get a palindrome (696).

It can be divided in two parts, 6 and 60, that added together give a palindrome (66).

The spelling of 660 in words is "six hundred sixty", and thus it is an aban number and an oban number.

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