21420649 has 2 divisors, whose sum is σ = 21420650. Its totient is φ = 21420648.

The previous prime is 21420643. The next prime is 21420661. The reversal of 21420649 is 94602412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17073424 + 4347225 = 4132^2 + 2085^2 .

It is a cyclic number.

It is not a de Polignac number, because 21420649 - 2⁹ = 21420137 is a prime.

It is not a weakly prime, because it can be changed into another prime (21420643) 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, 10710324 + 10710325.

It is an arithmetic number, because the mean of its divisors is an integer number (10710325).

Almost surely, 2^21420649 is an apocalyptic number.

It is an amenable number.

21420649 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420649 is an equidigital number, since it uses as much as digits as its factorization.

21420649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 21420649 is about 4628.2446996675. The cubic root of 21420649 is about 277.7223778170.

The spelling of 21420649 in words is "twenty-one million, four hundred twenty thousand, six hundred forty-nine".