20212681 has 4 divisors (see below), whose sum is σ = 20909700. Its totient is φ = 19515664.

The previous prime is 20212667. The next prime is 20212691. The reversal of 20212681 is 18621202.

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 4372281 + 15840400 = 2091^2 + 3980^2 .

It is a cyclic number.

It is not a de Polignac number, because 20212681 - 2¹⁷ = 20081609 is a prime.

It is a super-2 number, since 2×20212681² = 817104946415522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20212691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 348466 + ... + 348523.

It is an arithmetic number, because the mean of its divisors is an integer number (5227425).

Almost surely, 2^20212681 is an apocalyptic number.

It is an amenable number.

20212681 is a deficient number, since it is larger than the sum of its proper divisors (697019).

20212681 is an equidigital number, since it uses as much as digits as its factorization.

20212681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 697018.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 20212681 is about 4495.8515322461. The cubic root of 20212681 is about 272.4005461495.

Adding to 20212681 its reverse (18621202), we get a palindrome (38833883).

The spelling of 20212681 in words is "twenty million, two hundred twelve thousand, six hundred eighty-one".