77840371561 has 4 divisors (see below), whose sum is σ = 78825692800. Its totient is φ = 76855050324.

The previous prime is 77840371501. The next prime is 77840371591. The reversal of 77840371561 is 16517304877.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16517304877 = 17159 ⋅962603.

It is a cyclic number.

It is not a de Polignac number, because 77840371561 - 2²³ = 77831982953 is a prime.

It is a super-4 number, since 4×77840371561⁴ (a number of 45 digits) contains 4444 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77840371501) 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, 492660501 + ... + 492660658.

It is an arithmetic number, because the mean of its divisors is an integer number (19706423200).

Almost surely, 2^77840371561 is an apocalyptic number.

It is an amenable number.

77840371561 is a deficient number, since it is larger than the sum of its proper divisors (985321239).

77840371561 is an equidigital number, since it uses as much as digits as its factorization.

77840371561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 985321238.

The product of its (nonzero) digits is 987840, while the sum is 49.

The spelling of 77840371561 in words is "seventy-seven billion, eight hundred forty million, three hundred seventy-one thousand, five hundred sixty-one".