1261609856640 has 768 divisors, whose sum is σ = 5160643488000. Its totient is φ = 277878472704.

The previous prime is 1261609856609. The next prime is 1261609856677. The reversal of 1261609856640 is 466589061621.

1261609856640 is a `hidden beast` number, since 1 + 26 + 1 + 609 + 8 + 5 + 6 + 6 + 4 + 0 = 666.

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, 1002072331 + ... + 1002073589.

It is an arithmetic number, because the mean of its divisors is an integer number (6719587875).

Almost surely, 2^{1261609856640} is an apocalyptic number.

1261609856640 is a gapful number since it is divisible by the number (10) 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 1261609856640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2580321744000).

1261609856640 is an abundant number, since it is smaller than the sum of its proper divisors (3899033631360).

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

1261609856640 is a wasteful number, since it uses less digits than its factorization.

1261609856640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2177 (or 2162 counting only the distinct ones).

The product of its (nonzero) digits is 3732480, while the sum is 54.

The spelling of 1261609856640 in words is "one trillion, two hundred sixty-one billion, six hundred nine million, eight hundred fifty-six thousand, six hundred forty".