217887121 has 9 divisors (see below), whose sum is σ = 226103761. Its totient is φ = 209960464.

The previous prime is 217887107. The next prime is 217887151. The reversal of 217887121 is 121788712.

The square root of 217887121 is 14761.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 27447121 + 190440000 = 5239^2 + 13800^2 .

It is a de Polignac number, because none of the positive numbers 2^k-217887121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217887101) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 427815 + ... + 428323.

Almost surely, 2^217887121 is an apocalyptic number.

217887121 is the 14761-st square number.

217887121 is the 7381-st centered octagonal number.

It is an amenable number.

217887121 is a deficient number, since it is larger than the sum of its proper divisors (8216640).

217887121 is an frugal number, since it uses more digits than its factorization.

217887121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1076 (or 538 counting only the distinct ones).

The product of its digits is 12544, while the sum is 37.

The cubic root of 217887121 is about 601.7422701867.

Multiplying 217887121 by its product of digits (12544), we get a square (2733176045824 = 1653232²).

The spelling of 217887121 in words is "two hundred seventeen million, eight hundred eighty-seven thousand, one hundred twenty-one".