1561956181 has 2 divisors, whose sum is σ = 1561956182. Its totient is φ = 1561956180.

The previous prime is 1561956127. The next prime is 1561956229. The reversal of 1561956181 is 1816591651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1079451025 + 482505156 = 32855^2 + 21966^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561956181 - 2¹¹ = 1561954133 is a prime.

It is a super-2 number, since 2×1561956181² = 4879414222728209522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561953181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780978090 + 780978091.

It is an arithmetic number, because the mean of its divisors is an integer number (780978091).

Almost surely, 2^1561956181 is an apocalyptic number.

It is an amenable number.

1561956181 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561956181 is an equidigital number, since it uses as much as digits as its factorization.

1561956181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64800, while the sum is 43.

The square root of 1561956181 is about 39521.5913267672. The cubic root of 1561956181 is about 1160.2625696247.

The spelling of 1561956181 in words is "one billion, five hundred sixty-one million, nine hundred fifty-six thousand, one hundred eighty-one".