161389721 has 8 divisors (see below), whose sum is σ = 173780640. Its totient is φ = 149320768.

The previous prime is 161389693. The next prime is 161389729. The reversal of 161389721 is 127983161.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161389721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161389729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79451 + ... + 81456.

It is an arithmetic number, because the mean of its divisors is an integer number (21722580).

Almost surely, 2^161389721 is an apocalyptic number.

It is an amenable number.

161389721 is a deficient number, since it is larger than the sum of its proper divisors (12390919).

161389721 is a wasteful number, since it uses less digits than its factorization.

161389721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160983.

The product of its digits is 18144, while the sum is 38.

The square root of 161389721 is about 12703.9254169725. The cubic root of 161389721 is about 544.4507790908.

The spelling of 161389721 in words is "one hundred sixty-one million, three hundred eighty-nine thousand, seven hundred twenty-one".