21438647 has 2 divisors, whose sum is σ = 21438648. Its totient is φ = 21438646.

The previous prime is 21438623. The next prime is 21438673. The reversal of 21438647 is 74683412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21438647 - 2¹⁶ = 21373111 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21438607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719323 + 10719324.

It is an arithmetic number, because the mean of its divisors is an integer number (10719324).

Almost surely, 2^21438647 is an apocalyptic number.

21438647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21438647 is an equidigital number, since it uses as much as digits as its factorization.

21438647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 35.

The square root of 21438647 is about 4630.1886570636. The cubic root of 21438647 is about 277.8001384251.

The spelling of 21438647 in words is "twenty-one million, four hundred thirty-eight thousand, six hundred forty-seven".