78829781 has 4 divisors (see below), whose sum is σ = 79553100. Its totient is φ = 78106464.

The previous prime is 78829759. The next prime is 78829787. The reversal of 78829781 is 18792887.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 51696100 + 27133681 = 7190^2 + 5209^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78829781 is a prime.

It is a super-2 number, since 2×78829781² = 12428268745015922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78829787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 361496 + ... + 361713.

It is an arithmetic number, because the mean of its divisors is an integer number (19888275).

Almost surely, 2^78829781 is an apocalyptic number.

It is an amenable number.

78829781 is a deficient number, since it is larger than the sum of its proper divisors (723319).

78829781 is a wasteful number, since it uses less digits than its factorization.

78829781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 723318.

The product of its digits is 451584, while the sum is 50.

The square root of 78829781 is about 8878.6136868320. The cubic root of 78829781 is about 428.7756427982.

The spelling of 78829781 in words is "seventy-eight million, eight hundred twenty-nine thousand, seven hundred eighty-one".