291439978 has 4 divisors (see below), whose sum is σ = 437159970. Its totient is φ = 145719988.

The previous prime is 291439957. The next prime is 291439979. The reversal of 291439978 is 879934192.

It is a happy number.

291439978 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 171164889 + 120275089 = 13083^2 + 10967^2 .

It is not an unprimeable number, because it can be changed into a prime (291439979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 72859993 + ... + 72859996.

Almost surely, 2^291439978 is an apocalyptic number.

291439978 is a deficient number, since it is larger than the sum of its proper divisors (145719992).

291439978 is a wasteful number, since it uses less digits than its factorization.

291439978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145719991.

The product of its digits is 979776, while the sum is 52.

The square root of 291439978 is about 17071.6132219542. The cubic root of 291439978 is about 663.0043458952.

The spelling of 291439978 in words is "two hundred ninety-one million, four hundred thirty-nine thousand, nine hundred seventy-eight".