777777661 has 8 divisors (see below), whose sum is σ = 782041400.
Its totient is φ = 773521920.
The previous prime is 777777653. The next prime is 777777677. The reversal of 777777661 is 166777777.
It is a happy number.
It is the 11386-th star number.
It can be written as a sum of positive squares in 4 ways, for example, as 213715161 + 564062500 = 14619^2 + 23750^2
It is a sphenic number, since it is the product of 3 distinct primes.
It is a cyclic number.
It is not a de Polignac number, because 777777661 - 23 = 777777653 is a prime.
It is a Duffinian number.
It is a nialpdrome in base 10.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (777777641) 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, 339841 + ... + 342121.
It is an arithmetic number, because the mean of its divisors is an integer number (97755175).
Almost surely, 2777777661 is an apocalyptic number.
It is an amenable number.
777777661 is a deficient number, since it is larger than the sum of its proper divisors (4263739).
777777661 is a wasteful number, since it uses less digits than its factorization.
777777661 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 3999.
The product of its digits is 4235364, while the sum is 55.
The square root of 777777661 is about 27888.6654574937.
The cubic root of 777777661 is about 919.6413461012.
The spelling of 777777661 in words is "seven hundred seventy-seven million, seven hundred seventy-seven thousand, six hundred sixty-one".