161277991 has 8 divisors (see below), whose sum is σ = 186914304. Its totient is φ = 136290840.

The previous prime is 161277979. The next prime is 161278003. The reversal of 161277991 is 199772161.

161277991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (161277979) and next prime (161278003).

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

It is not a de Polignac number, because 161277991 - 2⁵ = 161277959 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 (161277901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161755 + ... + 162748.

It is an arithmetic number, because the mean of its divisors is an integer number (23364288).

Almost surely, 2^161277991 is an apocalyptic number.

161277991 is a deficient number, since it is larger than the sum of its proper divisors (25636313).

161277991 is an equidigital number, since it uses as much as digits as its factorization.

161277991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324581.

The product of its digits is 47628, while the sum is 43.

The square root of 161277991 is about 12699.5271959235. The cubic root of 161277991 is about 544.3251091113.

The spelling of 161277991 in words is "one hundred sixty-one million, two hundred seventy-seven thousand, nine hundred ninety-one".