661388 has 48 divisors (see below), whose sum is σ = 1505280. Its totient is φ = 247104.

The previous prime is 661373. The next prime is 661393. The reversal of 661388 is 883166.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661388.

It is an unprimeable number.

661388 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 15 ways as a sum of consecutive naturals, for example, 8333 + ... + 8411.

It is an arithmetic number, because the mean of its divisors is an integer number (31360).

2⁶⁶¹³⁸⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (752640).

661388 is an abundant number, since it is smaller than the sum of its proper divisors (843892).

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

661388 is a wasteful number, since it uses less digits than its factorization.

661388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126 (or 124 counting only the distinct ones).

The product of its digits is 6912, while the sum is 32.

The square root of 661388 is about 813.2576467516. The cubic root of 661388 is about 87.1268682353.

The spelling of 661388 in words is "six hundred sixty-one thousand, three hundred eighty-eight".