1561072861 has 2 divisors, whose sum is σ = 1561072862. Its totient is φ = 1561072860.

The previous prime is 1561072853. The next prime is 1561072879. The reversal of 1561072861 is 1682701651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1561040100 + 32761 = 39510^2 + 181^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561072861 - 2³ = 1561072853 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1561072861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561072831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780536430 + 780536431.

It is an arithmetic number, because the mean of its divisors is an integer number (780536431).

Almost surely, 2^1561072861 is an apocalyptic number.

It is an amenable number.

1561072861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561072861 is an equidigital number, since it uses as much as digits as its factorization.

1561072861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 37.

The square root of 1561072861 is about 39510.4145890675. The cubic root of 1561072861 is about 1160.0438105233.

The spelling of 1561072861 in words is "one billion, five hundred sixty-one million, seventy-two thousand, eight hundred sixty-one".