21221210237 has 2 divisors, whose sum is σ = 21221210238. Its totient is φ = 21221210236.

The previous prime is 21221210191. The next prime is 21221210261. The reversal of 21221210237 is 73201212212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19172833156 + 2048377081 = 138466^2 + 45259^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221210237 - 2¹⁸ = 21220948093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221210137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610605118 + 10610605119.

It is an arithmetic number, because the mean of its divisors is an integer number (10610605119).

Almost surely, 2^21221210237 is an apocalyptic number.

It is an amenable number.

21221210237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221210237 is an equidigital number, since it uses as much as digits as its factorization.

21221210237 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 23.

Adding to 21221210237 its reverse (73201212212), we get a palindrome (94422422449).

The spelling of 21221210237 in words is "twenty-one billion, two hundred twenty-one million, two hundred ten thousand, two hundred thirty-seven".