21000737 has 2 divisors, whose sum is σ = 21000738. Its totient is φ = 21000736.

The previous prime is 21000731. The next prime is 21000739. The reversal of 21000737 is 73700012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18181696 + 2819041 = 4264^2 + 1679^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000737 - 2⁶ = 21000673 is a prime.

Together with 21000739, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21000731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500368 + 10500369.

It is an arithmetic number, because the mean of its divisors is an integer number (10500369).

Almost surely, 2^21000737 is an apocalyptic number.

It is an amenable number.

21000737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000737 is an equidigital number, since it uses as much as digits as its factorization.

21000737 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 294, while the sum is 20.

The square root of 21000737 is about 4582.6561075429. The cubic root of 21000737 is about 275.8956451037.

Adding to 21000737 its reverse (73700012), we get a palindrome (94700749).

The spelling of 21000737 in words is "twenty-one million, seven hundred thirty-seven", and thus it is an aban number.