1561641181 has 2 divisors, whose sum is σ = 1561641182. Its totient is φ = 1561641180.

The previous prime is 1561641083. The next prime is 1561641241. The reversal of 1561641181 is 1811461651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1250683225 + 310957956 = 35365^2 + 17634^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1561641181 is a prime.

It is a super-2 number, since 2×1561641181² = 4877446356390149522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561641481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780820590 + 780820591.

It is an arithmetic number, because the mean of its divisors is an integer number (780820591).

Almost surely, 2^1561641181 is an apocalyptic number.

It is an amenable number.

1561641181 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561641181 is an equidigital number, since it uses as much as digits as its factorization.

1561641181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5760, while the sum is 34.

The square root of 1561641181 is about 39517.6059624062. The cubic root of 1561641181 is about 1160.1845675899.

The spelling of 1561641181 in words is "one billion, five hundred sixty-one million, six hundred forty-one thousand, one hundred eighty-one".