21530237 has 2 divisors, whose sum is σ = 21530238. Its totient is φ = 21530236.

The previous prime is 21530233. The next prime is 21530251. The reversal of 21530237 is 73203512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19945156 + 1585081 = 4466^2 + 1259^2 .

It is a cyclic number.

It is not a de Polignac number, because 21530237 - 2² = 21530233 is a prime.

It is a super-2 number, since 2×21530237² = 927102210552338, 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 (21530233) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765118 + 10765119.

It is an arithmetic number, because the mean of its divisors is an integer number (10765119).

Almost surely, 2^21530237 is an apocalyptic number.

It is an amenable number.

21530237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21530237 is an equidigital number, since it uses as much as digits as its factorization.

21530237 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1260, while the sum is 23.

The square root of 21530237 is about 4640.0686417337. The cubic root of 21530237 is about 278.1951814979.

Adding to 21530237 its reverse (73203512), we get a palindrome (94733749).

The spelling of 21530237 in words is "twenty-one million, five hundred thirty thousand, two hundred thirty-seven".