20988221 has 2 divisors, whose sum is σ = 20988222. Its totient is φ = 20988220.

The previous prime is 20988211. The next prime is 20988299. The reversal of 20988221 is 12288902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20839225 + 148996 = 4565^2 + 386^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20988221 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 (20988211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10494110 + 10494111.

It is an arithmetic number, because the mean of its divisors is an integer number (10494111).

Almost surely, 2^20988221 is an apocalyptic number.

It is an amenable number.

20988221 is a deficient number, since it is larger than the sum of its proper divisors (1).

20988221 is an equidigital number, since it uses as much as digits as its factorization.

20988221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 20988221 is about 4581.2903204228. The cubic root of 20988221 is about 275.8408248671.

The spelling of 20988221 in words is "twenty million, nine hundred eighty-eight thousand, two hundred twenty-one".