161781447827 has 4 divisors (see below), whose sum is σ = 162203854080. Its totient is φ = 161359041576.

The previous prime is 161781447823. The next prime is 161781447833. The reversal of 161781447827 is 728744187161.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 161781447827 - 2² = 161781447823 is a prime.

It is a super-2 number, since 2×161781447827² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161781447823) 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, 211202552 + ... + 211203317.

It is an arithmetic number, because the mean of its divisors is an integer number (40550963520).

Almost surely, 2^161781447827 is an apocalyptic number.

161781447827 is a deficient number, since it is larger than the sum of its proper divisors (422406253).

161781447827 is an equidigital number, since it uses as much as digits as its factorization.

161781447827 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 422406252.

The product of its digits is 4214784, while the sum is 56.

The spelling of 161781447827 in words is "one hundred sixty-one billion, seven hundred eighty-one million, four hundred forty-seven thousand, eight hundred twenty-seven".