20856541 has 2 divisors, whose sum is σ = 20856542. Its totient is φ = 20856540.

The previous prime is 20856491. The next prime is 20856551. The reversal of 20856541 is 14565802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17189316 + 3667225 = 4146^2 + 1915^2 .

It is a cyclic number.

It is not a de Polignac number, because 20856541 - 2⁹ = 20856029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20856551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10428270 + 10428271.

It is an arithmetic number, because the mean of its divisors is an integer number (10428271).

Almost surely, 2^20856541 is an apocalyptic number.

It is an amenable number.

20856541 is a deficient number, since it is larger than the sum of its proper divisors (1).

20856541 is an equidigital number, since it uses as much as digits as its factorization.

20856541 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 20856541 is about 4566.8962107760. The cubic root of 20856541 is about 275.2627395280.

The spelling of 20856541 in words is "twenty million, eight hundred fifty-six thousand, five hundred forty-one".