6399994 has 4 divisors (see below), whose sum is σ = 9599994. Its totient is φ = 3199996.

The previous prime is 6399971. The next prime is 6400013. The reversal of 6399994 is 4999936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 3560769 + 2839225 = 1887^2 + 1685^2 .

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1599997 + ... + 1600000.

Almost surely, 2^6399994 is an apocalyptic number.

6399994 is a deficient number, since it is larger than the sum of its proper divisors (3200000).

6399994 is a wasteful number, since it uses less digits than its factorization.

6399994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3199999.

The product of its digits is 472392, while the sum is 49.

The square root of 6399994 is about 2529.8209422803. The cubic root of 6399994 is about 185.6634953246.

The spelling of 6399994 in words is "six million, three hundred ninety-nine thousand, nine hundred ninety-four".