77720161 has 8 divisors (see below), whose sum is σ = 79725800. Its totient is φ = 75738240.

The previous prime is 77720147. The next prime is 77720173. The reversal of 77720161 is 16102777.

It can be written as a sum of positive squares in 4 ways, for example, as 20430400 + 57289761 = 4520^2 + 7569^2 .

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 77720161 - 2¹⁹ = 77195873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77720191) 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, 805 + ... + 12493.

It is an arithmetic number, because the mean of its divisors is an integer number (9965725).

Almost surely, 2^77720161 is an apocalyptic number.

It is an amenable number.

77720161 is a deficient number, since it is larger than the sum of its proper divisors (2005639).

77720161 is a wasteful number, since it uses less digits than its factorization.

77720161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11859.

The product of its (nonzero) digits is 4116, while the sum is 31.

The square root of 77720161 is about 8815.9038674432. The cubic root of 77720161 is about 426.7542915599.

The spelling of 77720161 in words is "seventy-seven million, seven hundred twenty thousand, one hundred sixty-one".