77991280 has 20 divisors (see below), whose sum is σ = 181329912. Its totient is φ = 31196480.

The previous prime is 77991253. The next prime is 77991313. The reversal of 77991280 is 8219977.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 487366 + ... + 487525.

Almost surely, 2^77991280 is an apocalyptic number.

It is an amenable number.

77991280 is an abundant number, since it is smaller than the sum of its proper divisors (103338632).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

77991280 is a wasteful number, since it uses less digits than its factorization.

77991280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 974904 (or 974898 counting only the distinct ones).

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 77991280 is about 8831.2671797427. The cubic root of 77991280 is about 427.2499455321.

The spelling of 77991280 in words is "seventy-seven million, nine hundred ninety-one thousand, two hundred eighty".