21509430 has 16 divisors (see below), whose sum is σ = 51622704. Its totient is φ = 5735840.

The previous prime is 21509419. The next prime is 21509447. The reversal of 21509430 is 3490512.

It is a self number, because there is not a number n which added to its sum of digits gives 21509430.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 358461 + ... + 358520.

It is an arithmetic number, because the mean of its divisors is an integer number (3226419).

Almost surely, 2^21509430 is an apocalyptic number.

21509430 is an abundant number, since it is smaller than the sum of its proper divisors (30113274).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21509430 is a wasteful number, since it uses less digits than its factorization.

21509430 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 716991.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21509430 is about 4637.8259993234. The cubic root of 21509430 is about 278.1055359017.

Adding to 21509430 its reverse (3490512), we get a palindrome (24999942).

The spelling of 21509430 in words is "twenty-one million, five hundred nine thousand, four hundred thirty".