1561697280 has 704 divisors, whose sum is σ = 6602803200. Its totient is φ = 345047040.

The previous prime is 1561697279. The next prime is 1561697287. The reversal of 1561697280 is 827961651.

1561697280 is a `hidden beast` number, since 1 + 5 + 616 + 9 + 7 + 28 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (704).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561697287) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 19768281 + ... + 19768359.

Almost surely, 2^1561697280 is an apocalyptic number.

1561697280 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 1561697280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3301401600).

1561697280 is an abundant number, since it is smaller than the sum of its proper divisors (5041105920).

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

1561697280 is a wasteful number, since it uses less digits than its factorization.

1561697280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 181440, while the sum is 45.

The square root of 1561697280 is about 39518.3157535844. The cubic root of 1561697280 is about 1160.1984599008.

It can be divided in two parts, 15616 and 97280, that added together give a square (112896 = 336²).

The spelling of 1561697280 in words is "one billion, five hundred sixty-one million, six hundred ninety-seven thousand, two hundred eighty".