161010721 has 3 divisors (see below), whose sum is σ = 161023411. Its totient is φ = 160998032.

The previous prime is 161010719. The next prime is 161010739. The reversal of 161010721 is 127010161.

The square root of 161010721 is 12689.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 17969121 + 143041600 = 4239^2 + 11960^2 .

It is not a de Polignac number, because 161010721 - 2¹ = 161010719 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161010121) 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 2 ways as a sum of consecutive naturals, for example, 6345 + ... + 19033.

Almost surely, 2^161010721 is an apocalyptic number.

161010721 is the 12689-th square number.

161010721 is the 6345-th centered octagonal number.

It is an amenable number.

161010721 is a deficient number, since it is larger than the sum of its proper divisors (12690).

161010721 is an frugal number, since it uses more digits than its factorization.

161010721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25378 (or 12689 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 19.

The cubic root of 161010721 is about 544.0242575418.

Adding to 161010721 its reverse (127010161), we get a palindrome (288020882).

The spelling of 161010721 in words is "one hundred sixty-one million, ten thousand, seven hundred twenty-one".