19708561 has 2 divisors, whose sum is σ = 19708562. Its totient is φ = 19708560.

The previous prime is 19708553. The next prime is 19708571. The reversal of 19708561 is 16580791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16248961 + 3459600 = 4031^2 + 1860^2 .

It is an emirp because it is prime and its reverse (16580791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19708561 - 2³ = 19708553 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19708561.

It is not a weakly prime, because it can be changed into another prime (19708501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9854280 + 9854281.

It is an arithmetic number, because the mean of its divisors is an integer number (9854281).

Almost surely, 2^19708561 is an apocalyptic number.

It is an amenable number.

19708561 is a deficient number, since it is larger than the sum of its proper divisors (1).

19708561 is an equidigital number, since it uses as much as digits as its factorization.

19708561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 37.

The square root of 19708561 is about 4439.4325087786. The cubic root of 19708561 is about 270.1168264435.

The spelling of 19708561 in words is "nineteen million, seven hundred eight thousand, five hundred sixty-one".