661890880 has 112 divisors (see below), whose sum is σ = 1845478656. Its totient is φ = 221368320.

The previous prime is 661890877. The next prime is 661890881. The reversal of 661890880 is 88098166.

661890880 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (112).

It is a self number, because there is not a number n which added to its sum of digits gives 661890880.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661890881) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 88237 + ... + 95443.

It is an arithmetic number, because the mean of its divisors is an integer number (16477488).

Almost surely, 2^661890880 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 661890880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (922739328).

661890880 is an abundant number, since it is smaller than the sum of its proper divisors (1183587776).

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

661890880 is a wasteful number, since it uses less digits than its factorization.

661890880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7272 (or 7262 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 46.

The square root of 661890880 is about 25727.2400385273. The cubic root of 661890880 is about 871.4894466630.

The spelling of 661890880 in words is "six hundred sixty-one million, eight hundred ninety thousand, eight hundred eighty".