1561781996 has 24 divisors (see below), whose sum is σ = 2776300800. Its totient is φ = 768645072.

The previous prime is 1561781939. The next prime is 1561781999. The reversal of 1561781996 is 6991871651.

It is not an unprimeable number, because it can be changed into a prime (1561781999) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57455 + ... + 80153.

It is an arithmetic number, because the mean of its divisors is an integer number (115679200).

Almost surely, 2^1561781996 is an apocalyptic number.

It is an amenable number.

1561781996 is a deficient number, since it is larger than the sum of its proper divisors (1214518804).

1561781996 is a wasteful number, since it uses less digits than its factorization.

1561781996 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22973 (or 22971 counting only the distinct ones).

The product of its digits is 816480, while the sum is 53.

The square root of 1561781996 is about 39519.3875964697. The cubic root of 1561781996 is about 1160.2194382720.

The spelling of 1561781996 in words is "one billion, five hundred sixty-one million, seven hundred eighty-one thousand, nine hundred ninety-six".