21006218437 has 2 divisors, whose sum is σ = 21006218438. Its totient is φ = 21006218436.

The previous prime is 21006218407. The next prime is 21006218473. The reversal of 21006218437 is 73481260012.

Together with next prime (21006218473) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20644229761 + 361988676 = 143681^2 + 19026^2 .

It is a cyclic number.

It is not a de Polignac number, because 21006218437 - 2¹¹ = 21006216389 is a prime.

It is a super-2 number, since 2×21006218437² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21006218407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503109218 + 10503109219.

It is an arithmetic number, because the mean of its divisors is an integer number (10503109219).

Almost surely, 2^21006218437 is an apocalyptic number.

It is an amenable number.

21006218437 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006218437 is an equidigital number, since it uses as much as digits as its factorization.

21006218437 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16128, while the sum is 34.

Adding to 21006218437 its reverse (73481260012), we get a palindrome (94487478449).

The spelling of 21006218437 in words is "twenty-one billion, six million, two hundred eighteen thousand, four hundred thirty-seven".