19993999 has 2 divisors, whose sum is σ = 19994000. Its totient is φ = 19993998.

The previous prime is 19993997. The next prime is 19994003. The reversal of 19993999 is 99939991.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19993999 - 2¹ = 19993997 is a prime.

Together with 19993997, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19993997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9996999 + 9997000.

It is an arithmetic number, because the mean of its divisors is an integer number (9997000).

Almost surely, 2^19993999 is an apocalyptic number.

19993999 is a deficient number, since it is larger than the sum of its proper divisors (1).

19993999 is an equidigital number, since it uses as much as digits as its factorization.

19993999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1594323, while the sum is 58.

The square root of 19993999 is about 4471.4649724671. The cubic root of 19993999 is about 271.4146102435.

It can be divided in two parts, 1999 and 3999, that multiplied together give a triangular number (7994001 = T₃₉₉₈).

The spelling of 19993999 in words is "nineteen million, nine hundred ninety-three thousand, nine hundred ninety-nine".