161720420399 has 4 divisors (see below), whose sum is σ = 162993809664. Its totient is φ = 160447031136.

The previous prime is 161720420369. The next prime is 161720420431. The reversal of 161720420399 is 993024027161.

161720420399 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 161720420399 - 2¹⁶ = 161720354863 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 (161720420359) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 636694442 + ... + 636694695.

It is an arithmetic number, because the mean of its divisors is an integer number (40748452416).

Almost surely, 2^161720420399 is an apocalyptic number.

161720420399 is a deficient number, since it is larger than the sum of its proper divisors (1273389265).

161720420399 is a wasteful number, since it uses less digits than its factorization.

161720420399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1273389264.

The product of its (nonzero) digits is 163296, while the sum is 44.

The spelling of 161720420399 in words is "one hundred sixty-one billion, seven hundred twenty million, four hundred twenty thousand, three hundred ninety-nine".