399171778 has 4 divisors (see below), whose sum is σ = 598757670. Its totient is φ = 199585888.

The previous prime is 399171749. The next prime is 399171809. The reversal of 399171778 is 877171993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877171993 = 19 ⋅46166947.

It can be written as a sum of positive squares in only one way, i.e., 364160889 + 35010889 = 19083^2 + 5917^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99792943 + ... + 99792946.

Almost surely, 2^399171778 is an apocalyptic number.

399171778 is a deficient number, since it is larger than the sum of its proper divisors (199585892).

399171778 is a wasteful number, since it uses less digits than its factorization.

399171778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199585891.

The product of its digits is 666792, while the sum is 52.

The square root of 399171778 is about 19979.2837208945. The cubic root of 399171778 is about 736.2974156862.

The spelling of 399171778 in words is "three hundred ninety-nine million, one hundred seventy-one thousand, seven hundred seventy-eight".