1216551606660 has 72 divisors (see below), whose sum is σ = 3974068589400. Its totient is φ = 299458856448.

The previous prime is 1216551606649. The next prime is 1216551606667. The reversal of 1216551606660 is 666061556121.

It can be written as a sum of positive squares in 4 ways, for example, as 129582720576 + 1086968886084 = 359976^2 + 1042578^2 .

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

It is not an unprimeable number, because it can be changed into a prime (1216551606667) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 259944585 + ... + 259949264.

It is an arithmetic number, because the mean of its divisors is an integer number (55195397075).

Almost surely, 2^{1216551606660} is an apocalyptic number.

1216551606660 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1216551606660 is an abundant number, since it is smaller than the sum of its proper divisors (2757516982740).

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

1216551606660 is a wasteful number, since it uses less digits than its factorization.

1216551606660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 519893877 (or 519893872 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 45.

The spelling of 1216551606660 in words is "one trillion, two hundred sixteen billion, five hundred fifty-one million, six hundred six thousand, six hundred sixty".