161555777 has 4 divisors (see below), whose sum is σ = 171059076. Its totient is φ = 152052480.

The previous prime is 161555759. The next prime is 161555813. The reversal of 161555777 is 777555161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 777555161 = 2011 ⋅386651.

It can be written as a sum of positive squares in 2 ways, for example, as 59969536 + 101586241 = 7744^2 + 10079^2 .

It is a cyclic number.

It is not a de Polignac number, because 161555777 - 2⁸ = 161555521 is a prime.

It is a super-2 number, since 2×161555777² = 52200538164147458, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161585777) 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, 4751624 + ... + 4751657.

It is an arithmetic number, because the mean of its divisors is an integer number (42764769).

Almost surely, 2^161555777 is an apocalyptic number.

161555777 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

It is an amenable number.

161555777 is a deficient number, since it is larger than the sum of its proper divisors (9503299).

161555777 is an equidigital number, since it uses as much as digits as its factorization.

161555777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9503298.

The product of its digits is 257250, while the sum is 44.

The square root of 161555777 is about 12710.4593544057. The cubic root of 161555777 is about 544.6374459325.

The spelling of 161555777 in words is "one hundred sixty-one million, five hundred fifty-five thousand, seven hundred seventy-seven".