661860 has 36 divisors (see below), whose sum is σ = 2008188. Its totient is φ = 176448.

The previous prime is 661849. The next prime is 661873. The reversal of 661860 is 68166.

It can be written as a sum of positive squares in 2 ways, for example, as 389376 + 272484 = 624^2 + 522^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

661860 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 11 ways as a sum of consecutive naturals, for example, 1659 + ... + 2018.

It is an arithmetic number, because the mean of its divisors is an integer number (55783).

2⁶⁶¹⁸⁶⁰ is an apocalyptic number.

661860 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661860 is an abundant number, since it is smaller than the sum of its proper divisors (1346328).

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

661860 is a wasteful number, since it uses less digits than its factorization.

661860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3692 (or 3687 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 661860 is about 813.5477859352. The cubic root of 661860 is about 87.1475893567.

It can be divided in two parts, 661 and 860, that added together give a square (1521 = 39²).

The spelling of 661860 in words is "six hundred sixty-one thousand, eight hundred sixty".