20866621 has 2 divisors, whose sum is σ = 20866622. Its totient is φ = 20866620.

The previous prime is 20866613. The next prime is 20866639. The reversal of 20866621 is 12666802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11655396 + 9211225 = 3414^2 + 3035^2 .

It is a cyclic number.

It is not a de Polignac number, because 20866621 - 2³ = 20866613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20866661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10433310 + 10433311.

It is an arithmetic number, because the mean of its divisors is an integer number (10433311).

Almost surely, 2^20866621 is an apocalyptic number.

It is an amenable number.

20866621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20866621 is an equidigital number, since it uses as much as digits as its factorization.

20866621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 20866621 is about 4567.9996716287. Note that the first 3 decimals coincide. The cubic root of 20866621 is about 275.3070773617.

The spelling of 20866621 in words is "twenty million, eight hundred sixty-six thousand, six hundred twenty-one".