20681281 has 4 divisors (see below), whose sum is σ = 20874672. Its totient is φ = 20487892.

The previous prime is 20681251. The next prime is 20681303. The reversal of 20681281 is 18218602.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18218602 = 2 ⋅9109301.

It is a cyclic number.

It is not a de Polignac number, because 20681281 - 2⁵ = 20681249 is a prime.

It is a super-2 number, since 2×20681281² = 855430767601922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20681201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 96535 + ... + 96748.

It is an arithmetic number, because the mean of its divisors is an integer number (5218668).

Almost surely, 2^20681281 is an apocalyptic number.

It is an amenable number.

20681281 is a deficient number, since it is larger than the sum of its proper divisors (193391).

20681281 is a wasteful number, since it uses less digits than its factorization.

20681281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193390.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 20681281 is about 4547.6676439687. The cubic root of 20681281 is about 274.4895478561.

Adding to 20681281 its reverse (18218602), we get a palindrome (38899883).

The spelling of 20681281 in words is "twenty million, six hundred eighty-one thousand, two hundred eighty-one".