161311821157 has 4 divisors (see below), whose sum is σ = 162016239820. Its totient is φ = 160607402496.

The previous prime is 161311821119. The next prime is 161311821163. The reversal of 161311821157 is 751128113161.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 751128113161 = 1453 ⋅516949837.

It can be written as a sum of positive squares in 2 ways, for example, as 66742655716 + 94569165441 = 258346^2 + 307521^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161311821157 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161311821857) 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, 352208988 + ... + 352209445.

It is an arithmetic number, because the mean of its divisors is an integer number (40504059955).

Almost surely, 2^161311821157 is an apocalyptic number.

It is an amenable number.

161311821157 is a deficient number, since it is larger than the sum of its proper divisors (704418663).

161311821157 is an equidigital number, since it uses as much as digits as its factorization.

161311821157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 704418662.

The product of its digits is 10080, while the sum is 37.

The spelling of 161311821157 in words is "one hundred sixty-one billion, three hundred eleven million, eight hundred twenty-one thousand, one hundred fifty-seven".