20840639 has 2 divisors, whose sum is σ = 20840640. Its totient is φ = 20840638.

The previous prime is 20840627. The next prime is 20840653. The reversal of 20840639 is 93604802.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20840639 - 2¹⁶ = 20775103 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20840609) 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, 10420319 + 10420320.

It is an arithmetic number, because the mean of its divisors is an integer number (10420320).

Almost surely, 2^20840639 is an apocalyptic number.

20840639 is a deficient number, since it is larger than the sum of its proper divisors (1).

20840639 is an equidigital number, since it uses as much as digits as its factorization.

20840639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10368, while the sum is 32.

The square root of 20840639 is about 4565.1548714146. The cubic root of 20840639 is about 275.1927640221.

The spelling of 20840639 in words is "twenty million, eight hundred forty thousand, six hundred thirty-nine".