999998639 has 2 divisors, whose sum is σ = 999998640. Its totient is φ = 999998638.

The previous prime is 999998627. The next prime is 999998641. The reversal of 999998639 is 936899999.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999998639 is a prime.

Together with 999998641, 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 (999998609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499999319 + 499999320.

It is an arithmetic number, because the mean of its divisors is an integer number (499999320).

Almost surely, 2^999998639 is an apocalyptic number.

999998639 is a deficient number, since it is larger than the sum of its proper divisors (1).

999998639 is an equidigital number, since it uses as much as digits as its factorization.

999998639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 76527504, while the sum is 71.

The square root of 999998639 is about 31622.7550823770. The cubic root of 999998639 is about 999.9995463331. Note that the first 3 decimals are identical.

The spelling of 999998639 in words is "nine hundred ninety-nine million, nine hundred ninety-eight thousand, six hundred thirty-nine".