3999999 has 16 divisors (see below), whose sum is σ = 5760000. Its totient is φ = 2461536.

The previous prime is 3999971. The next prime is 4000037. The reversal of 3999999 is 9999993.

It is a Cunningham number, because it is equal to 2000²-1.

It is not a de Polignac number, because 3999999 - 2⁷ = 3999871 is a prime.

It is a D-number.

3999999 is a modest number, since divided by 9999 gives 399 as remainder.

3999999 is a lucky number.

It is a plaindrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3999929) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1002 + ... + 3000.

It is an arithmetic number, because the mean of its divisors is an integer number (360000).

Almost surely, 2^3999999 is an apocalyptic number.

3999999 is a deficient number, since it is larger than the sum of its proper divisors (1760001).

3999999 is a wasteful number, since it uses less digits than its factorization.

3999999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2054.

The product of its digits is 1594323, while the sum is 57.

The square root of 3999999 is about 1999.9997500000. Note that the first 3 decimals coincide. The cubic root of 3999999 is about 158.7400919685.

The spelling of 3999999 in words is "three million, nine hundred ninety-nine thousand, nine hundred ninety-nine".