399942217 has 4 divisors (see below), whose sum is σ = 400436176. Its totient is φ = 399448260.

The previous prime is 399942211. The next prime is 399942227. The reversal of 399942217 is 712249993.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 399942217 - 2⁷ = 399942089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399942211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 245763 + ... + 247384.

It is an arithmetic number, because the mean of its divisors is an integer number (100109044).

Almost surely, 2^399942217 is an apocalyptic number.

It is an amenable number.

399942217 is a deficient number, since it is larger than the sum of its proper divisors (493959).

399942217 is an equidigital number, since it uses as much as digits as its factorization.

399942217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 493958.

The product of its digits is 244944, while the sum is 46.

The square root of 399942217 is about 19998.5553728263. Note that the first 3 decimals coincide. The cubic root of 399942217 is about 736.7708189542.

The spelling of 399942217 in words is "three hundred ninety-nine million, nine hundred forty-two thousand, two hundred seventeen".