661800 has 48 divisors (see below), whose sum is σ = 2053440. Its totient is φ = 176320.

The previous prime is 661777. The next prime is 661823. The reversal of 661800 is 8166.

It is an interprime number because it is at equal distance from previous prime (661777) and next prime (661823).

It is an unprimeable number.

661800 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 11 ways as a sum of consecutive naturals, for example, 49 + ... + 1151.

It is an arithmetic number, because the mean of its divisors is an integer number (42780).

2⁶⁶¹⁸⁰⁰ is an apocalyptic number.

661800 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 661800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1026720).

661800 is an abundant number, since it is smaller than the sum of its proper divisors (1391640).

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

661800 is a wasteful number, since it uses less digits than its factorization.

661800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1122 (or 1113 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 661800 is about 813.5109095765. The cubic root of 661800 is about 87.1449558625.

Adding to 661800 its reverse (8166), we get a palindrome (669966).

The spelling of 661800 in words is "six hundred sixty-one thousand, eight hundred".