161718551 has 4 divisors (see below), whose sum is σ = 161866272. Its totient is φ = 161570832.

The previous prime is 161718541. The next prime is 161718553. The reversal of 161718551 is 155817161.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 155817161 = 4253 ⋅36637.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161718551 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 (161718553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 72206 + ... + 74411.

It is an arithmetic number, because the mean of its divisors is an integer number (40466568).

Almost surely, 2^161718551 is an apocalyptic number.

161718551 is a deficient number, since it is larger than the sum of its proper divisors (147721).

161718551 is a wasteful number, since it uses less digits than its factorization.

161718551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 147720.

The product of its digits is 8400, while the sum is 35.

The square root of 161718551 is about 12716.8608941043. The cubic root of 161718551 is about 544.8202993102.

The spelling of 161718551 in words is "one hundred sixty-one million, seven hundred eighteen thousand, five hundred fifty-one".