21816499 has 2 divisors, whose sum is σ = 21816500. Its totient is φ = 21816498.

The previous prime is 21816493. The next prime is 21816539. The reversal of 21816499 is 99461812.

It is an a-pointer prime, because the next prime (21816539) can be obtained adding 21816499 to its sum of digits (40).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21816499 - 2⁹ = 21815987 is a prime.

It is not a weakly prime, because it can be changed into another prime (21816493) 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, 10908249 + 10908250.

It is an arithmetic number, because the mean of its divisors is an integer number (10908250).

Almost surely, 2^21816499 is an apocalyptic number.

21816499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21816499 is an equidigital number, since it uses as much as digits as its factorization.

21816499 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 40.

The square root of 21816499 is about 4670.8135265711. The cubic root of 21816499 is about 279.4227008588.

The spelling of 21816499 in words is "twenty-one million, eight hundred sixteen thousand, four hundred ninety-nine".