161721671 has 16 divisors (see below), whose sum is σ = 173734848. Its totient is φ = 150163200.

The previous prime is 161721647. The next prime is 161721691. The reversal of 161721671 is 176127161.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161721671 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 (161721641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 298661 + ... + 299201.

It is an arithmetic number, because the mean of its divisors is an integer number (10858428).

Almost surely, 2^161721671 is an apocalyptic number.

161721671 is a deficient number, since it is larger than the sum of its proper divisors (12013177).

161721671 is a wasteful number, since it uses less digits than its factorization.

161721671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 922.

The product of its digits is 3528, while the sum is 32.

The square root of 161721671 is about 12716.9835652957. The cubic root of 161721671 is about 544.8238029866.

The spelling of 161721671 in words is "one hundred sixty-one million, seven hundred twenty-one thousand, six hundred seventy-one".