2117681 has 4 divisors (see below), whose sum is σ = 2123364. Its totient is φ = 2112000.

The previous prime is 2117677. The next prime is 2117699. The reversal of 2117681 is 1867112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1343281 + 774400 = 1159^2 + 880^2 .

It is a cyclic number.

It is not a de Polignac number, because 2117681 - 2² = 2117677 is a prime.

It is a super-2 number, since 2×2117681² = 8969145635522, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 7.

It is a self number, because there is not a number n which added to its sum of digits gives 2117681.

It is not an unprimeable number, because it can be changed into a prime (2117611) 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, 2240 + ... + 3041.

It is an arithmetic number, because the mean of its divisors is an integer number (530841).

2^2117681 is an apocalyptic number.

It is an amenable number.

2117681 is a deficient number, since it is larger than the sum of its proper divisors (5683).

2117681 is an equidigital number, since it uses as much as digits as its factorization.

2117681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5682.

The product of its digits is 672, while the sum is 26.

The square root of 2117681 is about 1455.2254120926. The cubic root of 2117681 is about 128.4163081029.

The spelling of 2117681 in words is "two million, one hundred seventeen thousand, six hundred eighty-one".