20851769 has 2 divisors, whose sum is σ = 20851770. Its totient is φ = 20851768.

The previous prime is 20851717. The next prime is 20851771. The reversal of 20851769 is 96715802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20839225 + 12544 = 4565^2 + 112^2 .

It is a cyclic number.

It is not a de Polignac number, because 20851769 - 2⁸ = 20851513 is a prime.

It is a super-2 number, since 2×20851769² = 869592540858722, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 20851771, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20851969) 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, 10425884 + 10425885.

It is an arithmetic number, because the mean of its divisors is an integer number (10425885).

Almost surely, 2^20851769 is an apocalyptic number.

It is an amenable number.

20851769 is a deficient number, since it is larger than the sum of its proper divisors (1).

20851769 is an equidigital number, since it uses as much as digits as its factorization.

20851769 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 20851769 is about 4566.3737253974. The cubic root of 20851769 is about 275.2417444520.

The spelling of 20851769 in words is "twenty million, eight hundred fifty-one thousand, seven hundred sixty-nine".