217871661 has 12 divisors (see below), whose sum is σ = 332098016. Its totient is φ = 124459440.

The previous prime is 217871659. The next prime is 217871671. The reversal of 217871661 is 166178712.

It is not a de Polignac number, because 217871661 - 2¹ = 217871659 is a prime.

It is a super-3 number, since 3×217871661³ (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 (217871671) 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 11 ways as a sum of consecutive naturals, for example, 66031 + ... + 69251.

Almost surely, 2^217871661 is an apocalyptic number.

217871661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

217871661 is a deficient number, since it is larger than the sum of its proper divisors (114226355).

217871661 is an frugal number, since it uses more digits than its factorization.

217871661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6452 (or 3231 counting only the distinct ones).

The product of its digits is 28224, while the sum is 39.

The square root of 217871661 is about 14760.4763134528. The cubic root of 217871661 is about 601.7280378088.

The spelling of 217871661 in words is "two hundred seventeen million, eight hundred seventy-one thousand, six hundred sixty-one".