21099389 has 4 divisors (see below), whose sum is σ = 21140256. Its totient is φ = 21058524.

The previous prime is 21099383. The next prime is 21099391. The reversal of 21099389 is 98399012.

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 21099389 - 2¹² = 21095293 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21099383) 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, 19649 + ... + 20694.

It is an arithmetic number, because the mean of its divisors is an integer number (5285064).

Almost surely, 2^21099389 is an apocalyptic number.

It is an amenable number.

21099389 is a deficient number, since it is larger than the sum of its proper divisors (40867).

21099389 is an equidigital number, since it uses as much as digits as its factorization.

21099389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40866.

The product of its (nonzero) digits is 34992, while the sum is 41.

The square root of 21099389 is about 4593.4071232583. The cubic root of 21099389 is about 276.3269815420.

It can be divided in two parts, 210 and 99389, that added together give a palindrome (99599).

The spelling of 21099389 in words is "twenty-one million, ninety-nine thousand, three hundred eighty-nine".