21958709 has 2 divisors, whose sum is σ = 21958710. Its totient is φ = 21958708.

The previous prime is 21958693. The next prime is 21958733. The reversal of 21958709 is 90785912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11035684 + 10923025 = 3322^2 + 3305^2 .

It is a cyclic number.

It is not a de Polignac number, because 21958709 - 2⁴ = 21958693 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21958759) 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, 10979354 + 10979355.

It is an arithmetic number, because the mean of its divisors is an integer number (10979355).

Almost surely, 2^21958709 is an apocalyptic number.

It is an amenable number.

21958709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21958709 is an equidigital number, since it uses as much as digits as its factorization.

21958709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 21958709 is about 4686.0120571761. The cubic root of 21958709 is about 280.0285217544.

The spelling of 21958709 in words is "twenty-one million, nine hundred fifty-eight thousand, seven hundred nine".