661000 has 32 divisors (see below), whose sum is σ = 1549080. Its totient is φ = 264000.

The previous prime is 660983. The next prime is 661009. The reversal of 661000 is 166.

It can be written as a sum of positive squares in 4 ways, for example, as 293764 + 367236 = 542^2 + 606^2 .

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (661009) by changing a digit.

661000 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 7 ways as a sum of consecutive naturals, for example, 670 + ... + 1330.

2⁶⁶¹⁰⁰⁰ 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 661000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (774540).

661000 is an abundant number, since it is smaller than the sum of its proper divisors (888080).

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

661000 is a wasteful number, since it uses less digits than its factorization.

661000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 682 (or 668 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 661000 is about 813.0190649671. The cubic root of 661000 is about 87.1098273871.

Adding to 661000 its reverse (166), we get a palindrome (661166).

The spelling of 661000 in words is "six hundred sixty-one thousand".