661121760 has 192 divisors, whose sum is σ = 2267092800. Its totient is φ = 160972800.

The previous prime is 661121759. The next prime is 661121767. The reversal of 661121760 is 67121166.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661121767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 629716 + ... + 630764.

It is an arithmetic number, because the mean of its divisors is an integer number (11807775).

Almost surely, 2^661121760 is an apocalyptic number.

661121760 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 661121760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1133546400).

661121760 is an abundant number, since it is smaller than the sum of its proper divisors (1605971040).

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

661121760 is a wasteful number, since it uses less digits than its factorization.

661121760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1181 (or 1173 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 661121760 is about 25712.2881128849. The cubic root of 661121760 is about 871.1517576904.

The spelling of 661121760 in words is "six hundred sixty-one million, one hundred twenty-one thousand, seven hundred sixty".