19994561 has 2 divisors, whose sum is σ = 19994562. Its totient is φ = 19994560.

The previous prime is 19994551. The next prime is 19994581. The reversal of 19994561 is 16549991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18447025 + 1547536 = 4295^2 + 1244^2 .

It is an emirp because it is prime and its reverse (16549991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19994561 - 2¹⁸ = 19732417 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19994531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9997280 + 9997281.

It is an arithmetic number, because the mean of its divisors is an integer number (9997281).

Almost surely, 2^19994561 is an apocalyptic number.

It is an amenable number.

19994561 is a deficient number, since it is larger than the sum of its proper divisors (1).

19994561 is an equidigital number, since it uses as much as digits as its factorization.

19994561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 87480, while the sum is 44.

The square root of 19994561 is about 4471.5278149644. The cubic root of 19994561 is about 271.4171532329.

The spelling of 19994561 in words is "nineteen million, nine hundred ninety-four thousand, five hundred sixty-one".