161377991 has 8 divisors (see below), whose sum is σ = 171057744. Its totient is φ = 151719040.

The previous prime is 161377981. The next prime is 161378023. The reversal of 161377991 is 199773161.

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 161377991 - 2²² = 157183687 is a prime.

It is a super-3 number, since 3×161377991³ (a number of 26 digits) contains 333 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 (161377981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12536 + ... + 21906.

It is an arithmetic number, because the mean of its divisors is an integer number (21382218).

Almost surely, 2^161377991 is an apocalyptic number.

161377991 is a deficient number, since it is larger than the sum of its proper divisors (9679753).

161377991 is a wasteful number, since it uses less digits than its factorization.

161377991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10401.

The product of its digits is 71442, while the sum is 44.

The square root of 161377991 is about 12703.4637402560. The cubic root of 161377991 is about 544.4375883244.

The spelling of 161377991 in words is "one hundred sixty-one million, three hundred seventy-seven thousand, nine hundred ninety-one".