21020420237 has 2 divisors, whose sum is σ = 21020420238. Its totient is φ = 21020420236.

The previous prime is 21020420227. The next prime is 21020420249. The reversal of 21020420237 is 73202402012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12217101961 + 8803318276 = 110531^2 + 93826^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020420237 - 2⁴ = 21020420221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020420227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510210118 + 10510210119.

It is an arithmetic number, because the mean of its divisors is an integer number (10510210119).

Almost surely, 2^21020420237 is an apocalyptic number.

It is an amenable number.

21020420237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020420237 is an equidigital number, since it uses as much as digits as its factorization.

21020420237 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 23.

Adding to 21020420237 its reverse (73202402012), we get a palindrome (94222822249).

The spelling of 21020420237 in words is "twenty-one billion, twenty million, four hundred twenty thousand, two hundred thirty-seven".