20111681 has 2 divisors, whose sum is σ = 20111682. Its totient is φ = 20111680.

The previous prime is 20111621. The next prime is 20111687. The reversal of 20111681 is 18611102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19439281 + 672400 = 4409^2 + 820^2 .

It is a cyclic number.

It is not a de Polignac number, because 20111681 - 2⁶ = 20111617 is a prime.

It is a super-2 number, since 2×20111681² = 808959425291522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20111687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10055840 + 10055841.

It is an arithmetic number, because the mean of its divisors is an integer number (10055841).

Almost surely, 2^20111681 is an apocalyptic number.

It is an amenable number.

20111681 is a deficient number, since it is larger than the sum of its proper divisors (1).

20111681 is an equidigital number, since it uses as much as digits as its factorization.

20111681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 20.

The square root of 20111681 is about 4484.6048878357. The cubic root of 20111681 is about 271.9460722456.

Adding to 20111681 its reverse (18611102), we get a palindrome (38722783).

The spelling of 20111681 in words is "twenty million, one hundred eleven thousand, six hundred eighty-one".