161721943 has 2 divisors, whose sum is σ = 161721944. Its totient is φ = 161721942.

The previous prime is 161721941. The next prime is 161721949. The reversal of 161721943 is 349127161.

It is a weak prime.

It is an emirp because it is prime and its reverse (349127161) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 161721943 - 2¹ = 161721941 is a prime.

Together with 161721941, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 161721899 and 161721908.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161721941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80860971 + 80860972.

It is an arithmetic number, because the mean of its divisors is an integer number (80860972).

Almost surely, 2^161721943 is an apocalyptic number.

161721943 is a deficient number, since it is larger than the sum of its proper divisors (1).

161721943 is an equidigital number, since it uses as much as digits as its factorization.

161721943 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 34.

The square root of 161721943 is about 12716.9942596511. The cubic root of 161721943 is about 544.8241084331.

The spelling of 161721943 in words is "one hundred sixty-one million, seven hundred twenty-one thousand, nine hundred forty-three".