1561245840 has 720 divisors, whose sum is σ = 6946430400. Its totient is φ = 322237440.

The previous prime is 1561245811. The next prime is 1561245841. The reversal of 1561245840 is 485421651.

It is a happy number.

1561245840 is a `hidden beast` number, since 1 + 56 + 1 + 24 + 584 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

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

It is a junction number, because it is equal to n+sod(n) for n = 1561245795 and 1561245804.

It is not an unprimeable number, because it can be changed into a prime (1561245841) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 10478086 + ... + 10478234.

It is an arithmetic number, because the mean of its divisors is an integer number (9647820).

It is a vampire number, since it can be written as 28161 ⋅ 55440 (with its own digits).

Almost surely, 2^1561245840 is an apocalyptic number.

1561245840 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 1561245840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3473215200).

1561245840 is an abundant number, since it is smaller than the sum of its proper divisors (5385184560).

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

1561245840 is a wasteful number, since it uses less digits than its factorization.

1561245840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 36.

The square root of 1561245840 is about 39512.6035588646. The cubic root of 1561245840 is about 1160.0866562294.

The spelling of 1561245840 in words is "one billion, five hundred sixty-one million, two hundred forty-five thousand, eight hundred forty".