21012137 has 2 divisors, whose sum is σ = 21012138. Its totient is φ = 21012136.

The previous prime is 21012127. The next prime is 21012151. The reversal of 21012137 is 73121012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20939776 + 72361 = 4576^2 + 269^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012137 - 2⁶ = 21012073 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21012127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506068 + 10506069.

It is an arithmetic number, because the mean of its divisors is an integer number (10506069).

Almost surely, 2^21012137 is an apocalyptic number.

It is an amenable number.

21012137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012137 is an equidigital number, since it uses as much as digits as its factorization.

21012137 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21012137 is about 4583.8997589389. The cubic root of 21012137 is about 275.9455582951.

Adding to 21012137 its reverse (73121012), we get a palindrome (94133149).

The spelling of 21012137 in words is "twenty-one million, twelve thousand, one hundred thirty-seven".