20781653 has 2 divisors, whose sum is σ = 20781654. Its totient is φ = 20781652.

The previous prime is 20781643. The next prime is 20781689. The reversal of 20781653 is 35618702.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10903204 + 9878449 = 3302^2 + 3143^2 .

It is a cyclic number.

It is not a de Polignac number, because 20781653 - 2⁴ = 20781637 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20781643) 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 as a sum of consecutive naturals, namely, 10390826 + 10390827.

It is an arithmetic number, because the mean of its divisors is an integer number (10390827).

Almost surely, 2^20781653 is an apocalyptic number.

It is an amenable number.

20781653 is a deficient number, since it is larger than the sum of its proper divisors (1).

20781653 is an equidigital number, since it uses as much as digits as its factorization.

20781653 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 20781653 is about 4558.6898337132. The cubic root of 20781653 is about 274.9328894089.

The spelling of 20781653 in words is "twenty million, seven hundred eighty-one thousand, six hundred fifty-three".