661812180 has 192 divisors, whose sum is σ = 2053201920. Its totient is φ = 158630400.

The previous prime is 661812169. The next prime is 661812187. The reversal of 661812180 is 81218166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661812187) 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 63 ways as a sum of consecutive naturals, for example, 2155587 + ... + 2155893.

It is an arithmetic number, because the mean of its divisors is an integer number (10693760).

Almost surely, 2^661812180 is an apocalyptic number.

661812180 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 661812180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1026600960).

661812180 is an abundant number, since it is smaller than the sum of its proper divisors (1391389740).

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

661812180 is a wasteful number, since it uses less digits than its factorization.

661812180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430 (or 428 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 33.

The square root of 661812180 is about 25725.7104858155. The cubic root of 661812180 is about 871.4549047468.

The spelling of 661812180 in words is "six hundred sixty-one million, eight hundred twelve thousand, one hundred eighty".