21509434 has 8 divisors (see below), whose sum is σ = 32284800. Its totient is φ = 10747836.

The previous prime is 21509419. The next prime is 21509447. The reversal of 21509434 is 43490512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

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, 2557 + ... + 7039.

It is an arithmetic number, because the mean of its divisors is an integer number (4035600).

Almost surely, 2^21509434 is an apocalyptic number.

21509434 is a deficient number, since it is larger than the sum of its proper divisors (10775366).

21509434 is a wasteful number, since it uses less digits than its factorization.

21509434 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6884.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21509434 is about 4637.8264305599. The cubic root of 21509434 is about 278.1055531410.

Adding to 21509434 its reverse (43490512), we get a palindrome (64999946).

The spelling of 21509434 in words is "twenty-one million, five hundred nine thousand, four hundred thirty-four".