1561641220 has 12 divisors (see below), whose sum is σ = 3279446604. Its totient is φ = 624656480.

The previous prime is 1561641181. The next prime is 1561641241. The reversal of 1561641220 is 221461651.

It can be written as a sum of positive squares in 2 ways, for example, as 313714944 + 1247926276 = 17712^2 + 35326^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39041011 + ... + 39041050.

It is an arithmetic number, because the mean of its divisors is an integer number (273287217).

Almost surely, 2^1561641220 is an apocalyptic number.

1561641220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1561641220 is an abundant number, since it is smaller than the sum of its proper divisors (1717805384).

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

1561641220 is a wasteful number, since it uses less digits than its factorization.

1561641220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78082070 (or 78082068 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 1561641220 is about 39517.6064558571. The cubic root of 1561641220 is about 1160.1845772479.

The spelling of 1561641220 in words is "one billion, five hundred sixty-one million, six hundred forty-one thousand, two hundred twenty".