21409019 has 4 divisors (see below), whose sum is σ = 21463344. Its totient is φ = 21354696.

The previous prime is 21409013. The next prime is 21409043. The reversal of 21409019 is 91090412.

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 21409019 - 2¹² = 21404923 is a prime.

It is a super-2 number, since 2×21409019² = 916692189084722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21409013) 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, 26567 + ... + 27360.

It is an arithmetic number, because the mean of its divisors is an integer number (5365836).

Almost surely, 2^21409019 is an apocalyptic number.

21409019 is a deficient number, since it is larger than the sum of its proper divisors (54325).

21409019 is an equidigital number, since it uses as much as digits as its factorization.

21409019 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54324.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21409019 is about 4626.9881132331. The cubic root of 21409019 is about 277.6721070716.

The spelling of 21409019 in words is "twenty-one million, four hundred nine thousand, nineteen".