20309281 has 2 divisors, whose sum is σ = 20309282. Its totient is φ = 20309280.

The previous prime is 20309269. The next prime is 20309297. The reversal of 20309281 is 18290302.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14592400 + 5716881 = 3820^2 + 2391^2 .

It is a cyclic number.

It is not a de Polignac number, because 20309281 - 2⁷ = 20309153 is a prime.

It is a super-2 number, since 2×20309281² = 824933789473922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20309381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10154640 + 10154641.

It is an arithmetic number, because the mean of its divisors is an integer number (10154641).

Almost surely, 2^20309281 is an apocalyptic number.

It is an amenable number.

20309281 is a deficient number, since it is larger than the sum of its proper divisors (1).

20309281 is an equidigital number, since it uses as much as digits as its factorization.

20309281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20309281 is about 4506.5819641941. The cubic root of 20309281 is about 272.8338069015.

Adding to 20309281 its reverse (18290302), we get a palindrome (38599583).

It can be divided in two parts, 2030 and 9281, that added together give a palindrome (11311).

The spelling of 20309281 in words is "twenty million, three hundred nine thousand, two hundred eighty-one".