661560 has 64 divisors (see below), whose sum is σ = 2052000. Its totient is φ = 170496.

The previous prime is 661553. The next prime is 661603. The reversal of 661560 is 65166.

661560 = T₉₅ + T₉₆ + ... + T₁₆₈.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 661560.

It is a congruent number.

It is an unprimeable number.

661560 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4366 + ... + 4514.

2⁶⁶¹⁵⁶⁰ is an apocalyptic number.

661560 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 661560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1026000).

661560 is an abundant number, since it is smaller than the sum of its proper divisors (1390440).

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

661560 is a wasteful number, since it uses less digits than its factorization.

661560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 661560 is about 813.3633874229. The cubic root of 661560 is about 87.1344202938.

It can be divided in two parts, 6615 and 60, that multiplied together give a square (396900 = 630²).

The spelling of 661560 in words is "six hundred sixty-one thousand, five hundred sixty".