21438505 has 8 divisors (see below), whose sum is σ = 28065024. Its totient is φ = 15591600.

The previous prime is 21438499. The next prime is 21438541. The reversal of 21438505 is 50583412.

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

It is not a de Polignac number, because 21438505 - 2¹⁹ = 20914217 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 194841 + ... + 194950.

It is an arithmetic number, because the mean of its divisors is an integer number (3508128).

Almost surely, 2^21438505 is an apocalyptic number.

It is an amenable number.

21438505 is a deficient number, since it is larger than the sum of its proper divisors (6626519).

21438505 is a wasteful number, since it uses less digits than its factorization.

21438505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 389807.

The product of its (nonzero) digits is 4800, while the sum is 28.

The square root of 21438505 is about 4630.1733228898. The cubic root of 21438505 is about 277.7995250825.

It can be divided in two parts, 2143 and 8505, that added together give a cube (10648 = 22³).

The spelling of 21438505 in words is "twenty-one million, four hundred thirty-eight thousand, five hundred five".