161981356465 has 8 divisors (see below), whose sum is σ = 195664897728. Its totient is φ = 128726905200.

The previous prime is 161981356429. The next prime is 161981356489. The reversal of 161981356465 is 564653189161.

It is a happy number.

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

It is not a de Polignac number, because 161981356465 - 2¹⁹ = 161980832177 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 107271667 + ... + 107273176.

It is an arithmetic number, because the mean of its divisors is an integer number (24458112216).

Almost surely, 2^161981356465 is an apocalyptic number.

It is an amenable number.

161981356465 is a deficient number, since it is larger than the sum of its proper divisors (33683541263).

161981356465 is a wasteful number, since it uses less digits than its factorization.

161981356465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214544999.

The product of its digits is 4665600, while the sum is 55.

The spelling of 161981356465 in words is "one hundred sixty-one billion, nine hundred eighty-one million, three hundred fifty-six thousand, four hundred sixty-five".