21005737 has 2 divisors, whose sum is σ = 21005738. Its totient is φ = 21005736.

The previous prime is 21005713. The next prime is 21005749. The reversal of 21005737 is 73750012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11451456 + 9554281 = 3384^2 + 3091^2 .

It is a cyclic number.

It is not a de Polignac number, because 21005737 - 2⁷ = 21005609 is a prime.

It is equal to p_1330297 and since 21005737 and 1330297 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21005707) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502868 + 10502869.

It is an arithmetic number, because the mean of its divisors is an integer number (10502869).

Almost surely, 2^21005737 is an apocalyptic number.

It is an amenable number.

21005737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005737 is an equidigital number, since it uses as much as digits as its factorization.

21005737 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1470, while the sum is 25.

The square root of 21005737 is about 4583.2016102284. The cubic root of 21005737 is about 275.9175390776.

Adding to 21005737 its reverse (73750012), we get a palindrome (94755749).

The spelling of 21005737 in words is "twenty-one million, five thousand, seven hundred thirty-seven".