21353639 has 2 divisors, whose sum is σ = 21353640. Its totient is φ = 21353638.

The previous prime is 21353627. The next prime is 21353711. The reversal of 21353639 is 93635312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21353639 - 2⁸ = 21353383 is a prime.

It is a Sophie Germain 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 (21353539) 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, 10676819 + 10676820.

It is an arithmetic number, because the mean of its divisors is an integer number (10676820).

Almost surely, 2^21353639 is an apocalyptic number.

21353639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21353639 is an equidigital number, since it uses as much as digits as its factorization.

21353639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14580, while the sum is 32.

The square root of 21353639 is about 4620.9997835966. Note that the first 3 decimals coincide. The cubic root of 21353639 is about 277.4324766046.

The spelling of 21353639 in words is "twenty-one million, three hundred fifty-three thousand, six hundred thirty-nine".