21438947 has 8 divisors (see below), whose sum is σ = 22331232. Its totient is φ = 20563200.

The previous prime is 21438931. The next prime is 21438953. The reversal of 21438947 is 74983412.

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

It is a cyclic number.

It is not a de Polignac number, because 21438947 - 2⁴ = 21438931 is a prime.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21438947.

It is not an unprimeable number, because it can be changed into a prime (21438647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1454 + ... + 6707.

It is an arithmetic number, because the mean of its divisors is an integer number (2791404).

Almost surely, 2^21438947 is an apocalyptic number.

21438947 is a deficient number, since it is larger than the sum of its proper divisors (892285).

21438947 is an equidigital number, since it uses as much as digits as its factorization.

21438947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8269.

The product of its digits is 48384, while the sum is 38.

The square root of 21438947 is about 4630.2210530384. The cubic root of 21438947 is about 277.8014342105.

The spelling of 21438947 in words is "twenty-one million, four hundred thirty-eight thousand, nine hundred forty-seven".