20721263 has 2 divisors, whose sum is σ = 20721264. Its totient is φ = 20721262.

The previous prime is 20721223. The next prime is 20721271. The reversal of 20721263 is 36212702.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20721263 - 2¹² = 20717167 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 (20721223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10360631 + 10360632.

It is an arithmetic number, because the mean of its divisors is an integer number (10360632).

Almost surely, 2^20721263 is an apocalyptic number.

20721263 is a deficient number, since it is larger than the sum of its proper divisors (1).

20721263 is an equidigital number, since it uses as much as digits as its factorization.

20721263 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 23.

The square root of 20721263 is about 4552.0614011676. The cubic root of 20721263 is about 274.6663192476. Note that the first 3 decimals are identical.

Adding to 20721263 its reverse (36212702), we get a palindrome (56933965).

The spelling of 20721263 in words is "twenty million, seven hundred twenty-one thousand, two hundred sixty-three".