213856681 has 4 divisors (see below), whose sum is σ = 215749332. Its totient is φ = 211964032.

The previous prime is 213856679. The next prime is 213856711. The reversal of 213856681 is 186658312.

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 93296281 + 120560400 = 9659^2 + 10980^2 .

It is a cyclic number.

It is not a de Polignac number, because 213856681 - 2¹ = 213856679 is a prime.

It is a super-2 number, since 2×213856681² = 91469360016671522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (211856681) 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, 946156 + ... + 946381.

It is an arithmetic number, because the mean of its divisors is an integer number (53937333).

Almost surely, 2^213856681 is an apocalyptic number.

It is an amenable number.

213856681 is a deficient number, since it is larger than the sum of its proper divisors (1892651).

213856681 is a wasteful number, since it uses less digits than its factorization.

213856681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1892650.

The product of its digits is 69120, while the sum is 40.

The square root of 213856681 is about 14623.8394753225. The cubic root of 213856681 is about 598.0088448485.

The spelling of 213856681 in words is "two hundred thirteen million, eight hundred fifty-six thousand, six hundred eighty-one".