661560665220 has 1440 divisors, whose sum is σ = 2789675513856. Its totient is φ = 127650816000.

The previous prime is 661560665179. The next prime is 661560665261. The reversal of 661560665220 is 22566065166.

It is a happy number.

661560665220 is a `hidden beast` number, since 6 + 6 + 1 + 5 + 60 + 66 + 522 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (661560665179) and next prime (661560665261).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 479 ways as a sum of consecutive naturals, for example, 1649777020 + ... + 1649777420.

Almost surely, 2^661560665220 is an apocalyptic number.

661560665220 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 661560665220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1394837756928).

661560665220 is an abundant number, since it is smaller than the sum of its proper divisors (2128114848636).

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

661560665220 is a wasteful number, since it uses less digits than its factorization.

661560665220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 511 (or 481 counting only the distinct ones).

The product of its (nonzero) digits is 777600, while the sum is 45.

The spelling of 661560665220 in words is "six hundred sixty-one billion, five hundred sixty million, six hundred sixty-five thousand, two hundred twenty".