2815681 has 4 divisors (see below), whose sum is σ = 3071664. Its totient is φ = 2559700.

The previous prime is 2815669. The next prime is 2815691. The reversal of 2815681 is 1865182.

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 not a de Polignac number, because 2815681 - 2⁵ = 2815649 is a prime.

It is a super-2 number, since 2×2815681² = 15856118987522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a Duffinian number.

2815681 is a lucky number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (2815691) 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, 127975 + ... + 127996.

It is an arithmetic number, because the mean of its divisors is an integer number (767916).

2^2815681 is an apocalyptic number.

It is an amenable number.

2815681 is a deficient number, since it is larger than the sum of its proper divisors (255983).

2815681 is a wasteful number, since it uses less digits than its factorization.

2815681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255982.

The product of its digits is 3840, while the sum is 31.

The square root of 2815681 is about 1677.9991060784. Note that the first 3 decimals coincide. The cubic root of 2815681 is about 141.2086009147.

The spelling of 2815681 in words is "two million, eight hundred fifteen thousand, six hundred eighty-one".