20866639 has 2 divisors, whose sum is σ = 20866640. Its totient is φ = 20866638.

The previous prime is 20866621. The next prime is 20866649. The reversal of 20866639 is 93666802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20866639 - 2⁷ = 20866511 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 (20866649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10433319 + 10433320.

It is an arithmetic number, because the mean of its divisors is an integer number (10433320).

Almost surely, 2^20866639 is an apocalyptic number.

20866639 is a deficient number, since it is larger than the sum of its proper divisors (1).

20866639 is an equidigital number, since it uses as much as digits as its factorization.

20866639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 93312, while the sum is 40.

The square root of 20866639 is about 4568.0016418561. The cubic root of 20866639 is about 275.3071565236.

The spelling of 20866639 in words is "twenty million, eight hundred sixty-six thousand, six hundred thirty-nine".