661320 has 96 divisors (see below), whose sum is σ = 2358720. Its totient is φ = 159360.

The previous prime is 661267. The next prime is 661321. The reversal of 661320 is 23166.

It is a happy number.

661320 is a `hidden beast` number, since 661 + 3 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 661293 and 661302.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661320.

It is not an unprimeable number, because it can be changed into a prime (661321) by changing a digit.

661320 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3877 + ... + 4043.

It is an arithmetic number, because the mean of its divisors is an integer number (24570).

2⁶⁶¹³²⁰ is an apocalyptic number.

661320 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 661320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1179360).

661320 is an abundant number, since it is smaller than the sum of its proper divisors (1697400).

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

661320 is a wasteful number, since it uses less digits than its factorization.

661320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195 (or 188 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 661320 is about 813.2158385078. The cubic root of 661320 is about 87.1238821767.

Adding to 661320 its reverse (23166), we get a palindrome (684486).

The spelling of 661320 in words is "six hundred sixty-one thousand, three hundred twenty".