161516721 has 8 divisors (see below), whose sum is σ = 215432704. Its totient is φ = 107639280.

The previous prime is 161516717. The next prime is 161516723. The reversal of 161516721 is 127615161.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 161516721 - 2² = 161516717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (161516723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2235 + ... + 18111.

It is an arithmetic number, because the mean of its divisors is an integer number (26929088).

Almost surely, 2^161516721 is an apocalyptic number.

It is an amenable number.

161516721 is a deficient number, since it is larger than the sum of its proper divisors (53915983).

161516721 is a wasteful number, since it uses less digits than its factorization.

161516721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19271.

The product of its digits is 2520, while the sum is 30.

The square root of 161516721 is about 12708.9228890571. The cubic root of 161516721 is about 544.5935538171.

It can be divided in two parts, 1615 and 16721, that added together give a triangular number (18336 = T₁₉₁).

The spelling of 161516721 in words is "one hundred sixty-one million, five hundred sixteen thousand, seven hundred twenty-one".