21253649 has 2 divisors, whose sum is σ = 21253650. Its totient is φ = 21253648.

The previous prime is 21253627. The next prime is 21253657. The reversal of 21253649 is 94635212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14326225 + 6927424 = 3785^2 + 2632^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253649 - 2¹⁶ = 21188113 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21253849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10626824 + 10626825.

It is an arithmetic number, because the mean of its divisors is an integer number (10626825).

Almost surely, 2^21253649 is an apocalyptic number.

It is an amenable number.

21253649 is a deficient number, since it is larger than the sum of its proper divisors (1).

21253649 is an equidigital number, since it uses as much as digits as its factorization.

21253649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 32.

The square root of 21253649 is about 4610.1680012772. The cubic root of 21253649 is about 276.9987662150.

The spelling of 21253649 in words is "twenty-one million, two hundred fifty-three thousand, six hundred forty-nine".