21320016637 has 2 divisors, whose sum is σ = 21320016638. Its totient is φ = 21320016636.

The previous prime is 21320016631. The next prime is 21320016649. The reversal of 21320016637 is 73661002312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14749130916 + 6570885721 = 121446^2 + 81061^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320016637 - 2¹⁹ = 21319492349 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21320016599 and 21320016608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21320016631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660008318 + 10660008319.

It is an arithmetic number, because the mean of its divisors is an integer number (10660008319).

Almost surely, 2^21320016637 is an apocalyptic number.

It is an amenable number.

21320016637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320016637 is an equidigital number, since it uses as much as digits as its factorization.

21320016637 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 31.

Adding to 21320016637 its reverse (73661002312), we get a palindrome (94981018949).

The spelling of 21320016637 in words is "twenty-one billion, three hundred twenty million, sixteen thousand, six hundred thirty-seven".