661605120 has 432 divisors, whose sum is σ = 2617235712. Its totient is φ = 152739840.

The previous prime is 661605107. The next prime is 661605149. The reversal of 661605120 is 21506166.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2914447 + ... + 2914673.

It is an arithmetic number, because the mean of its divisors is an integer number (6058416).

Almost surely, 2^661605120 is an apocalyptic number.

661605120 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 661605120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1308617856).

661605120 is an abundant number, since it is smaller than the sum of its proper divisors (1955630592).

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

661605120 is a wasteful number, since it uses less digits than its factorization.

661605120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288 (or 271 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 661605120 is about 25721.6857923426. The cubic root of 661605120 is about 871.3640117514.

The spelling of 661605120 in words is "six hundred sixty-one million, six hundred five thousand, one hundred twenty".