21320309761 has 2 divisors, whose sum is σ = 21320309762. Its totient is φ = 21320309760.

The previous prime is 21320309753. The next prime is 21320309779. The reversal of 21320309761 is 16790302312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15069035536 + 6251274225 = 122756^2 + 79065^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320309761 - 2³ = 21320309753 is a prime.

It is not a weakly prime, because it can be changed into another prime (21320307761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660154880 + 10660154881.

It is an arithmetic number, because the mean of its divisors is an integer number (10660154881).

Almost surely, 2^21320309761 is an apocalyptic number.

It is an amenable number.

21320309761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320309761 is an equidigital number, since it uses as much as digits as its factorization.

21320309761 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13608, while the sum is 34.

The spelling of 21320309761 in words is "twenty-one billion, three hundred twenty million, three hundred nine thousand, seven hundred sixty-one".