1561111578 has 96 divisors (see below), whose sum is σ = 3777725952. Its totient is φ = 462672000.

The previous prime is 1561111571. The next prime is 1561111579. The reversal of 1561111578 is 8751111651.

1561111578 is a `hidden beast` number, since 1 + 561 + 11 + 15 + 78 = 666.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1561111571) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2226628 + ... + 2227328.

It is an arithmetic number, because the mean of its divisors is an integer number (39351312).

Almost surely, 2^1561111578 is an apocalyptic number.

1561111578 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1561111578, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1888862976).

1561111578 is an abundant number, since it is smaller than the sum of its proper divisors (2216614374).

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

1561111578 is a wasteful number, since it uses less digits than its factorization.

1561111578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1060 (or 1057 counting only the distinct ones).

The product of its digits is 8400, while the sum is 36.

The square root of 1561111578 is about 39510.9045454543. The cubic root of 1561111578 is about 1160.0534007323.

The spelling of 1561111578 in words is "one billion, five hundred sixty-one million, one hundred eleven thousand, five hundred seventy-eight".