21389019 has 4 divisors (see below), whose sum is σ = 28518696. Its totient is φ = 14259344.

The previous prime is 21388993. The next prime is 21389021. The reversal of 21389019 is 91098312.

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

It is a cyclic number.

It is not a de Polignac number, because 21389019 - 2⁵ = 21388987 is a prime.

It is a super-2 number, since 2×21389019² = 914980267564722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21389059) 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, 3564834 + ... + 3564839.

It is an arithmetic number, because the mean of its divisors is an integer number (7129674).

Almost surely, 2^21389019 is an apocalyptic number.

21389019 is a deficient number, since it is larger than the sum of its proper divisors (7129677).

21389019 is an equidigital number, since it uses as much as digits as its factorization.

21389019 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7129676.

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 21389019 is about 4624.8263751194. The cubic root of 21389019 is about 277.5856143594.

The spelling of 21389019 in words is "twenty-one million, three hundred eighty-nine thousand, nineteen".