21578043 has 4 divisors (see below), whose sum is σ = 28770728. Its totient is φ = 14385360.

The previous prime is 21578033. The next prime is 21578093. The reversal of 21578043 is 34087512.

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

It is not a de Polignac number, because 21578043 - 2¹⁶ = 21512507 is a prime.

It is a super-2 number, since 2×21578043² = 931223879419698, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21578043.

It is not an unprimeable number, because it can be changed into a prime (21578003) 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 3 ways as a sum of consecutive naturals, for example, 3596338 + ... + 3596343.

It is an arithmetic number, because the mean of its divisors is an integer number (7192682).

Almost surely, 2^21578043 is an apocalyptic number.

21578043 is a deficient number, since it is larger than the sum of its proper divisors (7192685).

21578043 is an equidigital number, since it uses as much as digits as its factorization.

21578043 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7192684.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 21578043 is about 4645.2172177413. The cubic root of 21578043 is about 278.4009319438.

The spelling of 21578043 in words is "twenty-one million, five hundred seventy-eight thousand, forty-three".