161178721 has 4 divisors (see below), whose sum is σ = 175831344. Its totient is φ = 146526100.

The previous prime is 161178709. The next prime is 161178727. The reversal of 161178721 is 127871161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 161178721 - 2¹⁹ = 160654433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161178727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7326295 + ... + 7326316.

It is an arithmetic number, because the mean of its divisors is an integer number (43957836).

Almost surely, 2^161178721 is an apocalyptic number.

161178721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

161178721 is a deficient number, since it is larger than the sum of its proper divisors (14652623).

161178721 is a wasteful number, since it uses less digits than its factorization.

161178721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14652622.

The product of its digits is 4704, while the sum is 34.

The square root of 161178721 is about 12695.6181810891. The cubic root of 161178721 is about 544.2134050000.

The spelling of 161178721 in words is "one hundred sixty-one million, one hundred seventy-eight thousand, seven hundred twenty-one".