21993889 has 8 divisors (see below), whose sum is σ = 22401920. Its totient is φ = 21588336.

The previous prime is 21993871. The next prime is 21993893. The reversal of 21993889 is 98839912.

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 21993889 - 2⁵ = 21993857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21993809) 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 7 ways as a sum of consecutive naturals, for example, 30667 + ... + 31375.

It is an arithmetic number, because the mean of its divisors is an integer number (2800240).

Almost surely, 2^21993889 is an apocalyptic number.

It is an amenable number.

21993889 is a deficient number, since it is larger than the sum of its proper divisors (408031).

21993889 is an equidigital number, since it uses as much as digits as its factorization.

21993889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1239.

The product of its digits is 279936, while the sum is 49.

The square root of 21993889 is about 4689.7642797906. The cubic root of 21993889 is about 280.1779863261.

The spelling of 21993889 in words is "twenty-one million, nine hundred ninety-three thousand, eight hundred eighty-nine".