21768649 has 8 divisors (see below), whose sum is σ = 25960320. Its totient is φ = 17847456.

The previous prime is 21768641. The next prime is 21768667. The reversal of 21768649 is 94686712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21768649 - 2³ = 21768641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21768641) 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 7 ways as a sum of consecutive naturals, for example, 67444 + ... + 67765.

It is an arithmetic number, because the mean of its divisors is an integer number (3245040).

Almost surely, 2^21768649 is an apocalyptic number.

It is an amenable number.

21768649 is a deficient number, since it is larger than the sum of its proper divisors (4191671).

21768649 is a wasteful number, since it uses less digits than its factorization.

21768649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135239.

The product of its digits is 145152, while the sum is 43.

The square root of 21768649 is about 4665.6884808140. The cubic root of 21768649 is about 279.2182659306.

The spelling of 21768649 in words is "twenty-one million, seven hundred sixty-eight thousand, six hundred forty-nine".