21440643 has 16 divisors (see below), whose sum is σ = 33067776. Its totient is φ = 12103200.

The previous prime is 21440609. The next prime is 21440647. The reversal of 21440643 is 34604412.

It is not a de Polignac number, because 21440643 - 2⁶ = 21440579 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21440647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4408 + ... + 7893.

It is an arithmetic number, because the mean of its divisors is an integer number (2066736).

Almost surely, 2^21440643 is an apocalyptic number.

21440643 is a deficient number, since it is larger than the sum of its proper divisors (11627133).

21440643 is a wasteful number, since it uses less digits than its factorization.

21440643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12394.

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 21440643 is about 4630.4041940202. The cubic root of 21440643 is about 277.8087594895.

The spelling of 21440643 in words is "twenty-one million, four hundred forty thousand, six hundred forty-three".