19990387 has 2 divisors, whose sum is σ = 19990388. Its totient is φ = 19990386.

The previous prime is 19990363. The next prime is 19990391. The reversal of 19990387 is 78309991.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19990387 is a prime.

It is not a weakly prime, because it can be changed into another prime (19990307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9995193 + 9995194.

It is an arithmetic number, because the mean of its divisors is an integer number (9995194).

Almost surely, 2^19990387 is an apocalyptic number.

19990387 is a deficient number, since it is larger than the sum of its proper divisors (1).

19990387 is an equidigital number, since it uses as much as digits as its factorization.

19990387 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 122472, while the sum is 46.

The square root of 19990387 is about 4471.0610597486. The cubic root of 19990387 is about 271.3982651956.

The spelling of 19990387 in words is "nineteen million, nine hundred ninety thousand, three hundred eighty-seven".