217561997 has 8 divisors (see below), whose sum is σ = 219032352. Its totient is φ = 216097200.

The previous prime is 217561987. The next prime is 217562003. The reversal of 217561997 is 799165712.

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 217561997 - 2⁶ = 217561933 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 (217561907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100547 + ... + 102687.

It is an arithmetic number, because the mean of its divisors is an integer number (27379044).

Almost surely, 2^217561997 is an apocalyptic number.

It is an amenable number.

217561997 is a deficient number, since it is larger than the sum of its proper divisors (1470355).

217561997 is a wasteful number, since it uses less digits than its factorization.

217561997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2779.

The product of its digits is 238140, while the sum is 47.

The square root of 217561997 is about 14749.9829491427. The cubic root of 217561997 is about 601.4428211825.

The spelling of 217561997 in words is "two hundred seventeen million, five hundred sixty-one thousand, nine hundred ninety-seven".