77821978 has 8 divisors (see below), whose sum is σ = 125712468. Its totient is φ = 35917824.

The previous prime is 77821973. The next prime is 77821979. The reversal of 77821978 is 87912877.

It can be written as a sum of positive squares in 2 ways, for example, as 56505289 + 21316689 = 7517^2 + 4617^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (77821973) 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, 1496551 + ... + 1496602.

Almost surely, 2^77821978 is an apocalyptic number.

77821978 is a deficient number, since it is larger than the sum of its proper divisors (47890490).

77821978 is a wasteful number, since it uses less digits than its factorization.

77821978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2993168.

The product of its digits is 395136, while the sum is 49.

The square root of 77821978 is about 8821.6765980170. The cubic root of 77821978 is about 426.9405661839.

The spelling of 77821978 in words is "seventy-seven million, eight hundred twenty-one thousand, nine hundred seventy-eight".