19855999 has 2 divisors, whose sum is σ = 19856000. Its totient is φ = 19855998.

The previous prime is 19855993. The next prime is 19856003. The reversal of 19855999 is 99955891.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19855999 - 2⁹ = 19855487 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19855993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9927999 + 9928000.

It is an arithmetic number, because the mean of its divisors is an integer number (9928000).

Almost surely, 2^19855999 is an apocalyptic number.

19855999 is a deficient number, since it is larger than the sum of its proper divisors (1).

19855999 is an equidigital number, since it uses as much as digits as its factorization.

19855999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1312200, while the sum is 55.

The square root of 19855999 is about 4456.0070691147. The cubic root of 19855999 is about 270.7887270969.

The spelling of 19855999 in words is "nineteen million, eight hundred fifty-five thousand, nine hundred ninety-nine".