20509543 has 2 divisors, whose sum is σ = 20509544. Its totient is φ = 20509542.

The previous prime is 20509523. The next prime is 20509547. The reversal of 20509543 is 34590502.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20509543 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20509547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10254771 + 10254772.

It is an arithmetic number, because the mean of its divisors is an integer number (10254772).

Almost surely, 2^20509543 is an apocalyptic number.

20509543 is a deficient number, since it is larger than the sum of its proper divisors (1).

20509543 is an equidigital number, since it uses as much as digits as its factorization.

20509543 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 20509543 is about 4528.7462945058. The cubic root of 20509543 is about 273.7276450821.

The spelling of 20509543 in words is "twenty million, five hundred nine thousand, five hundred forty-three".