21520043 has 4 divisors (see below), whose sum is σ = 21564720. Its totient is φ = 21475368.

The previous prime is 21520021. The next prime is 21520061. The reversal of 21520043 is 34002512.

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 21520043 - 2²⁴ = 4742827 is a prime.

It is a super-2 number, since 2×21520043² = 926224501443698, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21520003) 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, 21608 + ... + 22581.

It is an arithmetic number, because the mean of its divisors is an integer number (5391180).

Almost surely, 2^21520043 is an apocalyptic number.

21520043 is a deficient number, since it is larger than the sum of its proper divisors (44677).

21520043 is an equidigital number, since it uses as much as digits as its factorization.

21520043 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44676.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21520043 is about 4638.9700365491. The cubic root of 21520043 is about 278.1512685369.

Adding to 21520043 its reverse (34002512), we get a palindrome (55522555).

The spelling of 21520043 in words is "twenty-one million, five hundred twenty thousand, forty-three".