161821793939 has 16 divisors (see below), whose sum is σ = 179915683584. Its totient is φ = 144535795200.

The previous prime is 161821793929. The next prime is 161821793941. The reversal of 161821793939 is 939397128161.

It is a cyclic number.

It is not a de Polignac number, because 161821793939 - 2¹⁶ = 161821728403 is a prime.

It is not an unprimeable number, because it can be changed into a prime (161821793909) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3507767 + ... + 3553599.

It is an arithmetic number, because the mean of its divisors is an integer number (11244730224).

Almost surely, 2^161821793939 is an apocalyptic number.

161821793939 is a deficient number, since it is larger than the sum of its proper divisors (18093889645).

161821793939 is a wasteful number, since it uses less digits than its factorization.

161821793939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54638.

The product of its digits is 4408992, while the sum is 59.

The spelling of 161821793939 in words is "one hundred sixty-one billion, eight hundred twenty-one million, seven hundred ninety-three thousand, nine hundred thirty-nine".