21930709 has 2 divisors, whose sum is σ = 21930710. Its totient is φ = 21930708.

The previous prime is 21930683. The next prime is 21930721. The reversal of 21930709 is 90703912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11881809 + 10048900 = 3447^2 + 3170^2 .

It is a cyclic number.

It is not a de Polignac number, because 21930709 - 2¹³ = 21922517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21930739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10965354 + 10965355.

It is an arithmetic number, because the mean of its divisors is an integer number (10965355).

Almost surely, 2^21930709 is an apocalyptic number.

It is an amenable number.

21930709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21930709 is an equidigital number, since it uses as much as digits as its factorization.

21930709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3402, while the sum is 31.

The square root of 21930709 is about 4683.0234891574. The cubic root of 21930709 is about 279.9094477593.

The spelling of 21930709 in words is "twenty-one million, nine hundred thirty thousand, seven hundred nine".