21643356737 has 2 divisors, whose sum is σ = 21643356738. Its totient is φ = 21643356736.

The previous prime is 21643356689. The next prime is 21643356751. The reversal of 21643356737 is 73765334612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12778945936 + 8864410801 = 113044^2 + 94151^2 .

It is a cyclic number.

It is not a de Polignac number, because 21643356737 - 2⁶ = 21643356673 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21643356691 and 21643356700.

It is not a weakly prime, because it can be changed into another prime (21643356767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821678368 + 10821678369.

It is an arithmetic number, because the mean of its divisors is an integer number (10821678369).

Almost surely, 2^21643356737 is an apocalyptic number.

It is an amenable number.

21643356737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21643356737 is an equidigital number, since it uses as much as digits as its factorization.

21643356737 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1905120, while the sum is 47.

The spelling of 21643356737 in words is "twenty-one billion, six hundred forty-three million, three hundred fifty-six thousand, seven hundred thirty-seven".