21443639 has 4 divisors (see below), whose sum is σ = 24507024. Its totient is φ = 18380256.

The previous prime is 21443629. The next prime is 21443657. The reversal of 21443639 is 93634412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21443639 - 2⁴ = 21443623 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21443629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1531682 + ... + 1531695.

It is an arithmetic number, because the mean of its divisors is an integer number (6126756).

Almost surely, 2^21443639 is an apocalyptic number.

21443639 is a deficient number, since it is larger than the sum of its proper divisors (3063385).

21443639 is an equidigital number, since it uses as much as digits as its factorization.

21443639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3063384.

The product of its digits is 15552, while the sum is 32.

The square root of 21443639 is about 4630.7276965937. The cubic root of 21443639 is about 277.8216987202.

The spelling of 21443639 in words is "twenty-one million, four hundred forty-three thousand, six hundred thirty-nine".