161681387749 has 8 divisors (see below), whose sum is σ = 186505633728. Its totient is φ = 137288868000.

The previous prime is 161681387723. The next prime is 161681387761. The reversal of 161681387749 is 947783186161.

161681387749 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 161681387749 - 2²³ = 161672999141 is a prime.

It is a super-2 number, since 2×161681387749² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161681387789) 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 7 ways as a sum of consecutive naturals, for example, 107930752 + ... + 107932249.

It is an arithmetic number, because the mean of its divisors is an integer number (23313204216).

Almost surely, 2^161681387749 is an apocalyptic number.

It is an amenable number.

161681387749 is a deficient number, since it is larger than the sum of its proper divisors (24824245979).

161681387749 is a wasteful number, since it uses less digits than its factorization.

161681387749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215863115.

The product of its digits is 12192768, while the sum is 61.

Multiplying 161681387749 by its sum of digits (61), we get a palindrome (9862564652689).

The spelling of 161681387749 in words is "one hundred sixty-one billion, six hundred eighty-one million, three hundred eighty-seven thousand, seven hundred forty-nine".