1800001561 has 2 divisors, whose sum is σ = 1800001562. Its totient is φ = 1800001560.

The previous prime is 1800001547. The next prime is 1800001579. The reversal of 1800001561 is 1651000081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1014040336 + 785961225 = 31844^2 + 28035^2 .

It is a cyclic number.

It is not a de Polignac number, because 1800001561 - 2¹³ = 1799993369 is a prime.

It is a zygodrome in base 3.

It is not a weakly prime, because it can be changed into another prime (1800001961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 900000780 + 900000781.

It is an arithmetic number, because the mean of its divisors is an integer number (900000781).

Almost surely, 2^1800001561 is an apocalyptic number.

It is an amenable number.

1800001561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1800001561 is an equidigital number, since it uses as much as digits as its factorization.

1800001561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 240, while the sum is 22.

The square root of 1800001561 is about 42426.4252677503. The cubic root of 1800001561 is about 1216.4407507560.

The spelling of 1800001561 in words is "one billion, eight hundred million, one thousand, five hundred sixty-one".