21117709 has 2 divisors, whose sum is σ = 21117710. Its totient is φ = 21117708.

The previous prime is 21117697. The next prime is 21117737. The reversal of 21117709 is 90771112.

It is an a-pointer prime, because the next prime (21117737) can be obtained adding 21117709 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13527684 + 7590025 = 3678^2 + 2755^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21117709 is a prime.

It is equal to p_1336933 and since 21117709 and 1336933 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21117739) 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, 10558854 + 10558855.

It is an arithmetic number, because the mean of its divisors is an integer number (10558855).

Almost surely, 2^21117709 is an apocalyptic number.

It is an amenable number.

21117709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21117709 is an equidigital number, since it uses as much as digits as its factorization.

21117709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 882, while the sum is 28.

The square root of 21117709 is about 4595.4008530269. The cubic root of 21117709 is about 276.4069340287.

The spelling of 21117709 in words is "twenty-one million, one hundred seventeen thousand, seven hundred nine".