77405811961 has 3 divisors (see below), whose sum is σ = 77406090181. Its totient is φ = 77405533742.

The previous prime is 77405811949. The next prime is 77405811971. The reversal of 77405811961 is 16911850477.

The square root of 77405811961 is 278219.

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: 16911850477 = 113063 ⋅149579.

It is not a de Polignac number, because 77405811961 - 2⁵ = 77405811929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77405811971) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 139110 + ... + 417328.

Almost surely, 2^77405811961 is an apocalyptic number.

77405811961 is the 278219-th square number.

77405811961 is the 139110-th centered octagonal number.

It is an amenable number.

77405811961 is a deficient number, since it is larger than the sum of its proper divisors (278220).

77405811961 is an frugal number, since it uses more digits than its factorization.

77405811961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556438 (or 278219 counting only the distinct ones).

The product of its (nonzero) digits is 423360, while the sum is 49.

Multiplying 77405811961 by its sum of digits (49), we get a square (3792884786089 = 1947533²).

The spelling of 77405811961 in words is "seventy-seven billion, four hundred five million, eight hundred eleven thousand, nine hundred sixty-one".