21406889 has 4 divisors (see below), whose sum is σ = 24465024. Its totient is φ = 18348756.

The previous prime is 21406883. The next prime is 21406897. The reversal of 21406889 is 98860412.

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 a de Polignac number, because none of the positive numbers 2^k-21406889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21406883) 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 3 ways as a sum of consecutive naturals, for example, 1529057 + ... + 1529070.

It is an arithmetic number, because the mean of its divisors is an integer number (6116256).

Almost surely, 2^21406889 is an apocalyptic number.

It is an amenable number.

21406889 is a deficient number, since it is larger than the sum of its proper divisors (3058135).

21406889 is an equidigital number, since it uses as much as digits as its factorization.

21406889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3058134.

The product of its (nonzero) digits is 27648, while the sum is 38.

The square root of 21406889 is about 4626.7579361795. The cubic root of 21406889 is about 277.6628981614.

The spelling of 21406889 in words is "twenty-one million, four hundred six thousand, eight hundred eighty-nine".