20127781 has 2 divisors, whose sum is σ = 20127782. Its totient is φ = 20127780.

The previous prime is 20127739. The next prime is 20127787. The reversal of 20127781 is 18772102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17355556 + 2772225 = 4166^2 + 1665^2 .

It is a cyclic number.

It is not a de Polignac number, because 20127781 - 2¹⁵ = 20095013 is a prime.

It is a super-2 number, since 2×20127781² = 810255135967922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20127787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10063890 + 10063891.

It is an arithmetic number, because the mean of its divisors is an integer number (10063891).

Almost surely, 2^20127781 is an apocalyptic number.

It is an amenable number.

20127781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20127781 is an equidigital number, since it uses as much as digits as its factorization.

20127781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1568, while the sum is 28.

The square root of 20127781 is about 4486.3995586662. The cubic root of 20127781 is about 272.0186198687.

Adding to 20127781 its reverse (18772102), we get a palindrome (38899883).

The spelling of 20127781 in words is "twenty million, one hundred twenty-seven thousand, seven hundred eighty-one".