21649893 has 4 divisors (see below), whose sum is σ = 28866528. Its totient is φ = 14433260.

The previous prime is 21649883. The next prime is 21649909. The reversal of 21649893 is 39894612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21649893 - 2⁵ = 21649861 is a prime.

It is a super-3 number, since 3×21649893³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21649883) 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 in 3 ways as a sum of consecutive naturals, for example, 3608313 + ... + 3608318.

It is an arithmetic number, because the mean of its divisors is an integer number (7216632).

Almost surely, 2^21649893 is an apocalyptic number.

It is an amenable number.

21649893 is a deficient number, since it is larger than the sum of its proper divisors (7216635).

21649893 is an equidigital number, since it uses as much as digits as its factorization.

21649893 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7216634.

The product of its digits is 93312, while the sum is 42.

The square root of 21649893 is about 4652.9445515716. The cubic root of 21649893 is about 278.7095936391.

The spelling of 21649893 in words is "twenty-one million, six hundred forty-nine thousand, eight hundred ninety-three".