21004000261 has 2 divisors, whose sum is σ = 21004000262. Its totient is φ = 21004000260.

The previous prime is 21004000229. The next prime is 21004000279. The reversal of 21004000261 is 16200040012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20081724100 + 922276161 = 141710^2 + 30369^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004000261 - 2⁵ = 21004000229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21004000561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502000130 + 10502000131.

It is an arithmetic number, because the mean of its divisors is an integer number (10502000131).

Almost surely, 2^21004000261 is an apocalyptic number.

It is an amenable number.

21004000261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004000261 is an equidigital number, since it uses as much as digits as its factorization.

21004000261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 16.

Adding to 21004000261 its reverse (16200040012), we get a palindrome (37204040273).

The spelling of 21004000261 in words is "twenty-one billion, four million, two hundred sixty-one", and thus it is an aban number.