1561978880 has 288 divisors, whose sum is σ = 4772869920. Its totient is φ = 485130240.

The previous prime is 1561978879. The next prime is 1561978907. The reversal of 1561978880 is 888791651.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5519219 + ... + 5519501.

It is an arithmetic number, because the mean of its divisors is an integer number (16572465).

Almost surely, 2^1561978880 is an apocalyptic number.

1561978880 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 1561978880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2386434960).

1561978880 is an abundant number, since it is smaller than the sum of its proper divisors (3210891040).

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

1561978880 is a wasteful number, since it uses less digits than its factorization.

1561978880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 335 (or 308 counting only the distinct ones).

The product of its (nonzero) digits is 967680, while the sum is 53.

The square root of 1561978880 is about 39521.8784978650. The cubic root of 1561978880 is about 1160.2681900710.

The spelling of 1561978880 in words is "one billion, five hundred sixty-one million, nine hundred seventy-eight thousand, eight hundred eighty".