19998691 has 2 divisors, whose sum is σ = 19998692. Its totient is φ = 19998690.

The previous prime is 19998683. The next prime is 19998701. The reversal of 19998691 is 19689991.

It is a weak prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 16986661 and 16668961.

It is a cyclic number.

It is not a de Polignac number, because 19998691 - 2³ = 19998683 is a prime.

It is not a weakly prime, because it can be changed into another prime (19998491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9999345 + 9999346.

It is an arithmetic number, because the mean of its divisors is an integer number (9999346).

Almost surely, 2^19998691 is an apocalyptic number.

19998691 is a deficient number, since it is larger than the sum of its proper divisors (1).

19998691 is an equidigital number, since it uses as much as digits as its factorization.

19998691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 314928, while the sum is 52.

The square root of 19998691 is about 4471.9896019557. The cubic root of 19998691 is about 271.4358395759.

The spelling of 19998691 in words is "nineteen million, nine hundred ninety-eight thousand, six hundred ninety-one".