661055220 has 288 divisors, whose sum is σ = 2462503680. Its totient is φ = 140175360.

The previous prime is 661055189. The next prime is 661055221. The reversal of 661055220 is 22550166.

661055220 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661055221) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1268560 + ... + 1269080.

It is an arithmetic number, because the mean of its divisors is an integer number (8550360).

Almost surely, 2^661055220 is an apocalyptic number.

661055220 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 661055220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1231251840).

661055220 is an abundant number, since it is smaller than the sum of its proper divisors (1801448460).

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

661055220 is a wasteful number, since it uses less digits than its factorization.

661055220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 615 (or 610 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 661055220 is about 25710.9941464736. The cubic root of 661055220 is about 871.1225304052.

The spelling of 661055220 in words is "six hundred sixty-one million, fifty-five thousand, two hundred twenty".