21018499 has 2 divisors, whose sum is σ = 21018500. Its totient is φ = 21018498.

The previous prime is 21018497. The next prime is 21018509. The reversal of 21018499 is 99481012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21018499 - 2¹ = 21018497 is a prime.

Together with 21018497, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21018497) 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, 10509249 + 10509250.

It is an arithmetic number, because the mean of its divisors is an integer number (10509250).

Almost surely, 2^21018499 is an apocalyptic number.

21018499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21018499 is an equidigital number, since it uses as much as digits as its factorization.

21018499 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 21018499 is about 4584.5936570213. The cubic root of 21018499 is about 275.9734055101.

The spelling of 21018499 in words is "twenty-one million, eighteen thousand, four hundred ninety-nine".