21081499 has 2 divisors, whose sum is σ = 21081500. Its totient is φ = 21081498.

The previous prime is 21081497. The next prime is 21081509. The reversal of 21081499 is 99418012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21081499 - 2¹ = 21081497 is a prime.

Together with 21081497, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21081491) 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, 10540749 + 10540750.

It is an arithmetic number, because the mean of its divisors is an integer number (10540750).

Almost surely, 2^21081499 is an apocalyptic number.

21081499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081499 is an equidigital number, since it uses as much as digits as its factorization.

21081499 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 21081499 is about 4591.4593540616. The cubic root of 21081499 is about 276.2488609932.

The spelling of 21081499 in words is "twenty-one million, eighty-one thousand, four hundred ninety-nine".