1561556656 has 20 divisors (see below), whose sum is σ = 3300563304. Its totient is φ = 709798400.

The previous prime is 1561556639. The next prime is 1561556671. The reversal of 1561556656 is 6566551651.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4436065 + ... + 4436416.

Almost surely, 2^1561556656 is an apocalyptic number.

1561556656 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

1561556656 is an abundant number, since it is smaller than the sum of its proper divisors (1739006648).

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

1561556656 is a wasteful number, since it uses less digits than its factorization.

1561556656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8872500 (or 8872494 counting only the distinct ones).

The product of its digits is 810000, while the sum is 46.

The square root of 1561556656 is about 39516.5364879059. The cubic root of 1561556656 is about 1160.1636352590.

The spelling of 1561556656 in words is "one billion, five hundred sixty-one million, five hundred fifty-six thousand, six hundred fifty-six".