661557960 has 384 divisors, whose sum is σ = 2657491200. Its totient is φ = 139345920.

The previous prime is 661557959. The next prime is 661557977. The reversal of 661557960 is 69755166.

661557960 is a `hidden beast` number, since 6 + 6 + 1 + 557 + 96 + 0 = 666.

661557960 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a hoax number, since the sum of its digits (45) 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 (45).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1962912 + ... + 1963248.

It is an arithmetic number, because the mean of its divisors is an integer number (6920550).

Almost surely, 2^661557960 is an apocalyptic number.

661557960 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 661557960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1328745600).

661557960 is an abundant number, since it is smaller than the sum of its proper divisors (1995933240).

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

661557960 is a wasteful number, since it uses less digits than its factorization.

661557960 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 421 (or 414 counting only the distinct ones).

The product of its (nonzero) digits is 340200, while the sum is 45.

The square root of 661557960 is about 25720.7690398246. The cubic root of 661557960 is about 871.3433073050.

The spelling of 661557960 in words is "six hundred sixty-one million, five hundred fifty-seven thousand, nine hundred sixty".