21438649 has 8 divisors (see below), whose sum is σ = 22935528. Its totient is φ = 19968000.

The previous prime is 21438647. The next prime is 21438673. The reversal of 21438649 is 94683412.

It can be written as a sum of positive squares in 4 ways, for example, as 672400 + 20766249 = 820^2 + 4557^2 .

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 21438649 - 2¹ = 21438647 is a prime.

It is a Duffinian number.

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

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, 4852 + ... + 8149.

It is an arithmetic number, because the mean of its divisors is an integer number (2866941).

Almost surely, 2^21438649 is an apocalyptic number.

It is an amenable number.

21438649 is a deficient number, since it is larger than the sum of its proper divisors (1496879).

21438649 is a wasteful number, since it uses less digits than its factorization.

21438649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13115.

The product of its digits is 41472, while the sum is 37.

The square root of 21438649 is about 4630.1888730375. The cubic root of 21438649 is about 277.8001470638.

The spelling of 21438649 in words is "twenty-one million, four hundred thirty-eight thousand, six hundred forty-nine".