1999561 has 2 divisors, whose sum is σ = 1999562. Its totient is φ = 1999560.

The previous prime is 1999559. The next prime is 1999567. The reversal of 1999561 is 1659991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1428025 + 571536 = 1195^2 + 756^2 .

It is a cyclic number.

It is not a de Polignac number, because 1999561 - 2¹ = 1999559 is a prime.

Together with 1999559, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1999567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999780 + 999781.

It is an arithmetic number, because the mean of its divisors is an integer number (999781).

2^1999561 is an apocalyptic number.

It is an amenable number.

1999561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1999561 is an equidigital number, since it uses as much as digits as its factorization.

1999561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21870, while the sum is 40.

The square root of 1999561 is about 1414.0583439165. The cubic root of 1999561 is about 125.9828858926.

The spelling of 1999561 in words is "one million, nine hundred ninety-nine thousand, five hundred sixty-one".