21643449 has 8 divisors (see below), whose sum is σ = 29561952. Its totient is φ = 14076960.

The previous prime is 21643429. The next prime is 21643507. The reversal of 21643449 is 94434612.

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

It is not a de Polignac number, because 21643449 - 2⁹ = 21642937 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21643429) 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, 87859 + ... + 88104.

It is an arithmetic number, because the mean of its divisors is an integer number (3695244).

Almost surely, 2^21643449 is an apocalyptic number.

It is an amenable number.

21643449 is a deficient number, since it is larger than the sum of its proper divisors (7918503).

21643449 is a wasteful number, since it uses less digits than its factorization.

21643449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176007.

The product of its digits is 20736, while the sum is 33.

The square root of 21643449 is about 4652.2520353051. The cubic root of 21643449 is about 278.6819386473.

The spelling of 21643449 in words is "twenty-one million, six hundred forty-three thousand, four hundred forty-nine".