661870 has 24 divisors (see below), whose sum is σ = 1311912. Its totient is φ = 240240.

The previous prime is 661849. The next prime is 661873. The reversal of 661870 is 78166.

661870 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661873) by changing a digit.

661870 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, 937 + ... + 1483.

It is an arithmetic number, because the mean of its divisors is an integer number (54663).

2⁶⁶¹⁸⁷⁰ is an apocalyptic number.

661870 is a deficient number, since it is larger than the sum of its proper divisors (650042).

661870 is a wasteful number, since it uses less digits than its factorization.

661870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 576 (or 565 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 661870 is about 813.5539318324. The cubic root of 661870 is about 87.1480282569.

It can be divided in two parts, 66 and 1870, that added together give a square (1936 = 44²).

The spelling of 661870 in words is "six hundred sixty-one thousand, eight hundred seventy".