1561351680 has 480 divisors, whose sum is σ = 6465523680. Its totient is φ = 356106240.

The previous prime is 1561351661. The next prime is 1561351717. The reversal of 1561351680 is 861531651.

1561351680 is a `hidden beast` number, since 1 + 5 + 61 + 3 + 516 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (480).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3386650 + ... + 3387110.

It is an arithmetic number, because the mean of its divisors is an integer number (13469841).

Almost surely, 2^1561351680 is an apocalyptic number.

1561351680 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 1561351680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3232761840).

1561351680 is an abundant number, since it is smaller than the sum of its proper divisors (4904172000).

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

1561351680 is an equidigital number, since it uses as much as digits as its factorization.

1561351680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 507 (or 478 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 1561351680 is about 39513.9428556554. The cubic root of 1561351680 is about 1160.1128705074.

The spelling of 1561351680 in words is "one billion, five hundred sixty-one million, three hundred fifty-one thousand, six hundred eighty".