217148981 has 4 divisors (see below), whose sum is σ = 248170272. Its totient is φ = 186127692.

The previous prime is 217148951. The next prime is 217148989. The reversal of 217148981 is 189841712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217148981 is a prime.

It is a super-2 number, since 2×217148981² = 94307359898676722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217148989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15510635 + ... + 15510648.

It is an arithmetic number, because the mean of its divisors is an integer number (62042568).

Almost surely, 2^217148981 is an apocalyptic number.

It is an amenable number.

217148981 is a deficient number, since it is larger than the sum of its proper divisors (31021291).

217148981 is an equidigital number, since it uses as much as digits as its factorization.

217148981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31021290.

The product of its digits is 32256, while the sum is 41.

The square root of 217148981 is about 14735.9757396652. The cubic root of 217148981 is about 601.0619904810.

The spelling of 217148981 in words is "two hundred seventeen million, one hundred forty-eight thousand, nine hundred eighty-one".