394781906 has 4 divisors (see below), whose sum is σ = 592172862. Its totient is φ = 197390952.

The previous prime is 394781879. The next prime is 394781909. The reversal of 394781906 is 609187493.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 609187493 = 43 ⋅14167151.

It can be written as a sum of positive squares in only one way, i.e., 304816681 + 89965225 = 17459^2 + 9485^2 .

It is a super-3 number, since 3×394781906³ (a number of 27 digits) contains 333 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (394781909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 98695475 + ... + 98695478.

Almost surely, 2^394781906 is an apocalyptic number.

394781906 is a deficient number, since it is larger than the sum of its proper divisors (197390956).

394781906 is a wasteful number, since it uses less digits than its factorization.

394781906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197390955.

The product of its (nonzero) digits is 326592, while the sum is 47.

The square root of 394781906 is about 19869.1194067578. The cubic root of 394781906 is about 733.5883287238.

The spelling of 394781906 in words is "three hundred ninety-four million, seven hundred eighty-one thousand, nine hundred six".