20687939 has 2 divisors, whose sum is σ = 20687940. Its totient is φ = 20687938.

The previous prime is 20687897. The next prime is 20687951. The reversal of 20687939 is 93978602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20687939 - 2⁸ = 20687683 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20687939.

It is not a weakly prime, because it can be changed into another prime (20687969) 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, 10343969 + 10343970.

It is an arithmetic number, because the mean of its divisors is an integer number (10343970).

Almost surely, 2^20687939 is an apocalyptic number.

20687939 is a deficient number, since it is larger than the sum of its proper divisors (1).

20687939 is an equidigital number, since it uses as much as digits as its factorization.

20687939 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 163296, while the sum is 44.

The square root of 20687939 is about 4548.3996086536. The cubic root of 20687939 is about 274.5190005019.

The spelling of 20687939 in words is "twenty million, six hundred eighty-seven thousand, nine hundred thirty-nine".