777991961 has 8 divisors (see below), whose sum is σ = 852162120. Its totient is φ = 706978048.

The previous prime is 777991937. The next prime is 777992011. The reversal of 777991961 is 169199777.

It can be written as a sum of positive squares in 4 ways, for example, as 304711936 + 473280025 = 17456^2 + 21755^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 777991961 - 2⁶ = 777991897 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 777991897 and 777991906.

It is not an unprimeable number, because it can be changed into a prime (777991661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 788546 + ... + 789531.

It is an arithmetic number, because the mean of its divisors is an integer number (106520265).

Almost surely, 2^777991961 is an apocalyptic number.

It is an amenable number.

777991961 is a deficient number, since it is larger than the sum of its proper divisors (74170159).

777991961 is a wasteful number, since it uses less digits than its factorization.

777991961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1578123.

The product of its digits is 1500282, while the sum is 56.

The square root of 777991961 is about 27892.5072555337. The cubic root of 777991961 is about 919.7258008465.

The spelling of 777991961 in words is "seven hundred seventy-seven million, nine hundred ninety-one thousand, nine hundred sixty-one".