661666000 has 80 divisors (see below), whose sum is σ = 1634181120. Its totient is φ = 258998400.

The previous prime is 661665971. The next prime is 661666009. The reversal of 661666000 is 666166.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661666009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 90481 + ... + 97519.

It is an arithmetic number, because the mean of its divisors is an integer number (20427264).

Almost surely, 2^661666000 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 661666000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (817090560).

661666000 is an abundant number, since it is smaller than the sum of its proper divisors (972515120).

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

661666000 is a wasteful number, since it uses less digits than its factorization.

661666000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7109 (or 7093 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 661666000 is about 25722.8692023266. The cubic root of 661666000 is about 871.3907381740.

The spelling of 661666000 in words is "six hundred sixty-one million, six hundred sixty-six thousand".