661500 has 144 divisors (see below), whose sum is σ = 2489760. Its totient is φ = 151200.

The previous prime is 661483. The next prime is 661513. The reversal of 661500 is 5166.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

661500 is a `hidden beast` number, since 661 + 5 + 0 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nialpdrome in base 15.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 94497 + ... + 94503.

It is an arithmetic number, because the mean of its divisors is an integer number (17290).

2⁶⁶¹⁵⁰⁰ is an apocalyptic number.

661500 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 661500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1244880).

661500 is an abundant number, since it is smaller than the sum of its proper divisors (1828260).

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

661500 is a wasteful number, since it uses less digits than its factorization.

661500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42 (or 17 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 661500 is about 813.3265027036. The cubic root of 661500 is about 87.1317860035.

Adding to 661500 its reverse (5166), we get a palindrome (666666).

The spelling of 661500 in words is "six hundred sixty-one thousand, five hundred".