21320307761 has 2 divisors, whose sum is σ = 21320307762. Its totient is φ = 21320307760.

The previous prime is 21320307731. The next prime is 21320307779. The reversal of 21320307761 is 16770302312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20764810000 + 555497761 = 144100^2 + 23569^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21320307761 is a prime.

It is not a weakly prime, because it can be changed into another prime (21320307731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660153880 + 10660153881.

It is an arithmetic number, because the mean of its divisors is an integer number (10660153881).

Almost surely, 2^21320307761 is an apocalyptic number.

It is an amenable number.

21320307761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320307761 is an equidigital number, since it uses as much as digits as its factorization.

21320307761 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10584, while the sum is 32.

The spelling of 21320307761 in words is "twenty-one billion, three hundred twenty million, three hundred seven thousand, seven hundred sixty-one".