199723987 has 2 divisors, whose sum is σ = 199723988. Its totient is φ = 199723986.

The previous prime is 199723967. The next prime is 199723999. The reversal of 199723987 is 789327991.

It is a strong prime.

It is an emirp because it is prime and its reverse (789327991) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199723987 is a prime.

It is not a weakly prime, because it can be changed into another prime (199723967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99861993 + 99861994.

It is an arithmetic number, because the mean of its divisors is an integer number (99861994).

Almost surely, 2^199723987 is an apocalyptic number.

199723987 is a deficient number, since it is larger than the sum of its proper divisors (1).

199723987 is an equidigital number, since it uses as much as digits as its factorization.

199723987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1714608, while the sum is 55.

The square root of 199723987 is about 14132.3737213534. The cubic root of 199723987 is about 584.5344014889.

The spelling of 199723987 in words is "one hundred ninety-nine million, seven hundred twenty-three thousand, nine hundred eighty-seven".