19886561 has 2 divisors, whose sum is σ = 19886562. Its totient is φ = 19886560.

The previous prime is 19886557. The next prime is 19886567. The reversal of 19886561 is 16568891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19855936 + 30625 = 4456^2 + 175^2 .

It is an emirp because it is prime and its reverse (16568891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19886561 - 2² = 19886557 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19886567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9943280 + 9943281.

It is an arithmetic number, because the mean of its divisors is an integer number (9943281).

Almost surely, 2^19886561 is an apocalyptic number.

It is an amenable number.

19886561 is a deficient number, since it is larger than the sum of its proper divisors (1).

19886561 is an equidigital number, since it uses as much as digits as its factorization.

19886561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 44.

The square root of 19886561 is about 4459.4350539054. The cubic root of 19886561 is about 270.9275869396.

The spelling of 19886561 in words is "nineteen million, eight hundred eighty-six thousand, five hundred sixty-one".