1561646656 has 56 divisors (see below), whose sum is σ = 3290962176. Its totient is φ = 732702720.

The previous prime is 1561646627. The next prime is 1561646683. The reversal of 1561646656 is 6566461651.

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 7 ways as a sum of consecutive naturals, for example, 397341 + ... + 401251.

Almost surely, 2^1561646656 is an apocalyptic number.

1561646656 is a gapful number since it is divisible by the number (16) 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 1561646656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1645481088).

1561646656 is an abundant number, since it is smaller than the sum of its proper divisors (1729315520).

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

1561646656 is a wasteful number, since it uses less digits than its factorization.

1561646656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4307 (or 4297 counting only the distinct ones).

The product of its digits is 777600, while the sum is 46.

The square root of 1561646656 is about 39517.6752352666. The cubic root of 1561646656 is about 1160.1859234291.

The spelling of 1561646656 in words is "one billion, five hundred sixty-one million, six hundred forty-six thousand, six hundred fifty-six".