77986561 has 3 divisors (see below), whose sum is σ = 77995393. Its totient is φ = 77977730.

The previous prime is 77986547. The next prime is 77986591. The reversal of 77986561 is 16568977.

The square root of 77986561 is 8831.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 16568977 = 2731 ⋅6067.

It is not a de Polignac number, because 77986561 - 2⁵ = 77986529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77986501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 4416 + ... + 13246.

Almost surely, 2^77986561 is an apocalyptic number.

77986561 is the 8831-st square number.

77986561 is the 4416-th centered octagonal number.

It is an amenable number.

77986561 is a deficient number, since it is larger than the sum of its proper divisors (8832).

77986561 is an frugal number, since it uses more digits than its factorization.

77986561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17662 (or 8831 counting only the distinct ones).

The product of its digits is 635040, while the sum is 49.

The cubic root of 77986561 is about 427.2413281877.

Multiplying 77986561 by its sum of digits (49), we get a square (3821341489 = 61817²).

The spelling of 77986561 in words is "seventy-seven million, nine hundred eighty-six thousand, five hundred sixty-one".