20721163 has 2 divisors, whose sum is σ = 20721164. Its totient is φ = 20721162.

The previous prime is 20721161. The next prime is 20721209. The reversal of 20721163 is 36112702.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20721163 - 2¹ = 20721161 is a prime.

Together with 20721161, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20721161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10360581 + 10360582.

It is an arithmetic number, because the mean of its divisors is an integer number (10360582).

Almost surely, 2^20721163 is an apocalyptic number.

20721163 is a deficient number, since it is larger than the sum of its proper divisors (1).

20721163 is an equidigital number, since it uses as much as digits as its factorization.

20721163 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 20721163 is about 4552.0504171197. The cubic root of 20721163 is about 274.6658774040.

Adding to 20721163 its reverse (36112702), we get a palindrome (56833865).

The spelling of 20721163 in words is "twenty million, seven hundred twenty-one thousand, one hundred sixty-three".