7782799978 has 4 divisors (see below), whose sum is σ = 11674199970. Its totient is φ = 3891399988.

The previous prime is 7782799967. The next prime is 7782799979. The reversal of 7782799978 is 8799972877.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8799972877 = 1423 ⋅6184099.

It can be written as a sum of positive squares in only one way, i.e., 5877215569 + 1905584409 = 76663^2 + 43653^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 7782799978.

It is not an unprimeable number, because it can be changed into a prime (7782799979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1945699993 + ... + 1945699996.

Almost surely, 2^7782799978 is an apocalyptic number.

7782799978 is a deficient number, since it is larger than the sum of its proper divisors (3891399992).

7782799978 is a wasteful number, since it uses less digits than its factorization.

7782799978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3891399991.

The product of its digits is 224042112, while the sum is 73.

The square root of 7782799978 is about 88220.1789728404. The cubic root of 7782799978 is about 1981.7336767776.

The spelling of 7782799978 in words is "seven billion, seven hundred eighty-two million, seven hundred ninety-nine thousand, nine hundred seventy-eight".