661805760 has 336 divisors, whose sum is σ = 2668584960. Its totient is φ = 137410560.

The previous prime is 661805747. The next prime is 661805761. The reversal of 661805760 is 67508166.

It is a tau number, because it is divible by the number of its divisors (336).

It is not an unprimeable number, because it can be changed into a prime (661805761) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 516801 + ... + 518079.

Almost surely, 2^661805760 is an apocalyptic number.

661805760 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 661805760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1334292480).

661805760 is an abundant number, since it is smaller than the sum of its proper divisors (2006779200).

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

661805760 is a wasteful number, since it uses less digits than its factorization.

661805760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1324 (or 1307 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 39.

The square root of 661805760 is about 25725.5857076180. The cubic root of 661805760 is about 871.4520868483.

The spelling of 661805760 in words is "six hundred sixty-one million, eight hundred five thousand, seven hundred sixty".