77516561 has 4 divisors (see below), whose sum is σ = 81596400. Its totient is φ = 73436724.

The previous prime is 77516539. The next prime is 77516563. The reversal of 77516561 is 16561577.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 77516561 - 2¹⁴ = 77500177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77516563) 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, 2039891 + ... + 2039928.

It is an arithmetic number, because the mean of its divisors is an integer number (20399100).

Almost surely, 2^77516561 is an apocalyptic number.

It is an amenable number.

77516561 is a deficient number, since it is larger than the sum of its proper divisors (4079839).

77516561 is a wasteful number, since it uses less digits than its factorization.

77516561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4079838.

The product of its digits is 44100, while the sum is 38.

The square root of 77516561 is about 8804.3489821792. The cubic root of 77516561 is about 426.3813160251.

The spelling of 77516561 in words is "seventy-seven million, five hundred sixteen thousand, five hundred sixty-one".