999983921 has 2 divisors, whose sum is σ = 999983922.
Its totient is φ = 999983920.
The previous prime is 999983893. The next prime is 999983923. The reversal of 999983921 is 129389999.
999983921 = 223602 + 223612.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 500014321 + 499969600 = 22361^2 + 22360^2
It is a cyclic number.
It is not a de Polignac number, because 999983921 - 226 = 932875057 is a prime.
Together with 999983923, it forms a pair of twin primes.
It is a Chen prime.
It is not a weakly prime, because it can be changed into another prime (999983923) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499991960 + 499991961.
It is an arithmetic number, because the mean of its divisors is an integer number (499991961).
Almost surely, 2999983921 is an apocalyptic number.
999983921 is the 22361-st centered square number.
It is an amenable number.
999983921 is a deficient number, since it is larger than the sum of its proper divisors (1).
999983921 is an equidigital number, since it uses as much as digits as its factorization.
999983921 is an evil number, because the sum of its binary digits is even.
The product of its digits is 2834352, while the sum is 59.
The square root of 999983921 is about 31622.5223693493.
The cubic root of 999983921 is about 999.9946403046.
The spelling of 999983921 in words is "nine hundred ninety-nine million, nine hundred eighty-three thousand, nine hundred twenty-one".