21001043 has 8 divisors (see below), whose sum is σ = 24775680. Its totient is φ = 17420040.

The previous prime is 21001037. The next prime is 21001049. The reversal of 21001043 is 34010012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21001037) and next prime (21001049).

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

It is a cyclic number.

It is not a de Polignac number, because 21001043 - 2²⁰ = 19952467 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001049) 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 7 ways as a sum of consecutive naturals, for example, 48173 + ... + 48606.

It is an arithmetic number, because the mean of its divisors is an integer number (3096960).

Almost surely, 2^21001043 is an apocalyptic number.

21001043 is a deficient number, since it is larger than the sum of its proper divisors (3774637).

21001043 is an equidigital number, since it uses as much as digits as its factorization.

21001043 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96817.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21001043 is about 4582.6894941726. The cubic root of 21001043 is about 275.8969851147.

Adding to 21001043 its reverse (34010012), we get a palindrome (55011055).

The spelling of 21001043 in words is "twenty-one million, one thousand, forty-three".