77987521 has 2 divisors, whose sum is σ = 77987522. Its totient is φ = 77987520.

The previous prime is 77987519. The next prime is 77987561. The reversal of 77987521 is 12578977.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56085121 + 21902400 = 7489^2 + 4680^2 .

It is a cyclic number.

It is not a de Polignac number, because 77987521 - 2¹ = 77987519 is a prime.

Together with 77987519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (77987501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38993760 + 38993761.

It is an arithmetic number, because the mean of its divisors is an integer number (38993761).

Almost surely, 2^77987521 is an apocalyptic number.

It is an amenable number.

77987521 is a deficient number, since it is larger than the sum of its proper divisors (1).

77987521 is an equidigital number, since it uses as much as digits as its factorization.

77987521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 246960, while the sum is 46.

The square root of 77987521 is about 8831.0543538130. The cubic root of 77987521 is about 427.2430812675.

The spelling of 77987521 in words is "seventy-seven million, nine hundred eighty-seven thousand, five hundred twenty-one".