21660499 has 12 divisors (see below), whose sum is σ = 26680104. Its totient is φ = 17473344.

The previous prime is 21660491. The next prime is 21660521. The reversal of 21660499 is 99406612.

It is not a de Polignac number, because 21660499 - 2³ = 21660491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660491) 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 in 11 ways as a sum of consecutive naturals, for example, 12169 + ... + 13834.

It is an arithmetic number, because the mean of its divisors is an integer number (2223342).

Almost surely, 2^21660499 is an apocalyptic number.

21660499 is a deficient number, since it is larger than the sum of its proper divisors (5019605).

21660499 is a wasteful number, since it uses less digits than its factorization.

21660499 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26034 (or 26027 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 21660499 is about 4654.0841204258. The cubic root of 21660499 is about 278.7550982732.

The spelling of 21660499 in words is "twenty-one million, six hundred sixty thousand, four hundred ninety-nine".