1561781760 has 640 divisors, whose sum is σ = 6599577600. Its totient is φ = 305233920.

The previous prime is 1561781693. The next prime is 1561781777. The reversal of 1561781760 is 671871651.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (640).

It is a hoax number, since the sum of its digits (42) 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 (42).

It is a congruent number.

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 63 ways as a sum of consecutive naturals, for example, 11235771 + ... + 11235909.

It is an arithmetic number, because the mean of its divisors is an integer number (10311840).

Almost surely, 2^1561781760 is an apocalyptic number.

1561781760 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 1561781760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3299788800).

1561781760 is an abundant number, since it is smaller than the sum of its proper divisors (5037795840).

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

1561781760 is a wasteful number, since it uses less digits than its factorization.

1561781760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 202 (or 186 counting only the distinct ones).

The product of its (nonzero) digits is 70560, while the sum is 42.

The square root of 1561781760 is about 39519.3846105933. The cubic root of 1561781760 is about 1160.2193798320.

The spelling of 1561781760 in words is "one billion, five hundred sixty-one million, seven hundred eighty-one thousand, seven hundred sixty".