21409519 has 4 divisors (see below), whose sum is σ = 21434544. Its totient is φ = 21384496.

The previous prime is 21409501. The next prime is 21409529. The reversal of 21409519 is 91590412.

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 21409519 - 2⁷ = 21409391 is a prime.

It is a super-2 number, since 2×21409519² = 916735007622722, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21409529) 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, 11182 + ... + 12955.

It is an arithmetic number, because the mean of its divisors is an integer number (5358636).

Almost surely, 2^21409519 is an apocalyptic number.

21409519 is a deficient number, since it is larger than the sum of its proper divisors (25025).

21409519 is an equidigital number, since it uses as much as digits as its factorization.

21409519 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25024.

The product of its (nonzero) digits is 3240, while the sum is 31.

The square root of 21409519 is about 4627.0421437458. The cubic root of 21409519 is about 277.6742686991.

The spelling of 21409519 in words is "twenty-one million, four hundred nine thousand, five hundred nineteen".