21243637 has 2 divisors, whose sum is σ = 21243638. Its totient is φ = 21243636.

The previous prime is 21243611. The next prime is 21243683. The reversal of 21243637 is 73634212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17522596 + 3721041 = 4186^2 + 1929^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21243637 is a prime.

It is a super-2 number, since 2×21243637² = 902584225975538, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21243137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621818 + 10621819.

It is an arithmetic number, because the mean of its divisors is an integer number (10621819).

Almost surely, 2^21243637 is an apocalyptic number.

It is an amenable number.

21243637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243637 is an equidigital number, since it uses as much as digits as its factorization.

21243637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 28.

The square root of 21243637 is about 4609.0820127223. The cubic root of 21243637 is about 276.9552639245.

Adding to 21243637 its reverse (73634212), we get a palindrome (94877849).

The spelling of 21243637 in words is "twenty-one million, two hundred forty-three thousand, six hundred thirty-seven".