21659849 has 4 divisors (see below), whose sum is σ = 22188180. Its totient is φ = 21131520.

The previous prime is 21659843. The next prime is 21659851. The reversal of 21659849 is 94895612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 499849 + 21160000 = 707^2 + 4600^2 .

It is a cyclic number.

It is not a de Polignac number, because 21659849 - 2⁸ = 21659593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21659843) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264104 + ... + 264185.

It is an arithmetic number, because the mean of its divisors is an integer number (5547045).

Almost surely, 2^21659849 is an apocalyptic number.

It is an amenable number.

21659849 is a deficient number, since it is larger than the sum of its proper divisors (528331).

21659849 is an equidigital number, since it uses as much as digits as its factorization.

21659849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 528330.

The product of its digits is 155520, while the sum is 44.

The square root of 21659849 is about 4654.0142887619. The cubic root of 21659849 is about 278.7523099006.

The spelling of 21659849 in words is "twenty-one million, six hundred fifty-nine thousand, eight hundred forty-nine".