399778 has 4 divisors (see below), whose sum is σ = 599670. Its totient is φ = 199888.

The previous prime is 399769. The next prime is 399781. The reversal of 399778 is 877993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877993 = 101 ⋅8693.

It can be written as a sum of positive squares in only one way, i.e., 368449 + 31329 = 607^2 + 177^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99943 + ... + 99946.

2³⁹⁹⁷⁷⁸ is an apocalyptic number.

399778 is a deficient number, since it is larger than the sum of its proper divisors (199892).

399778 is a wasteful number, since it uses less digits than its factorization.

399778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199891.

The product of its digits is 95256, while the sum is 43.

The square root of 399778 is about 632.2800012653. The cubic root of 399778 is about 73.6669965338. Note that the first 3 decimals are identical.

The spelling of 399778 in words is "three hundred ninety-nine thousand, seven hundred seventy-eight".