21043001 has 6 divisors (see below), whose sum is σ = 24478650. Its totient is φ = 18036816.

The previous prime is 21042997. The next prime is 21043007. The reversal of 21043001 is 10034012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15642025 + 5400976 = 3955^2 + 2324^2 .

It is not a de Polignac number, because 21043001 - 2² = 21042997 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21043007) 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 5 ways as a sum of consecutive naturals, for example, 214676 + ... + 214773.

It is an arithmetic number, because the mean of its divisors is an integer number (4079775).

Almost surely, 2^21043001 is an apocalyptic number.

It is an amenable number.

21043001 is a deficient number, since it is larger than the sum of its proper divisors (3435649).

21043001 is an equidigital number, since it uses as much as digits as its factorization.

21043001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 429463 (or 429456 counting only the distinct ones).

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

The square root of 21043001 is about 4587.2650893534. The cubic root of 21043001 is about 276.0806011532.

Adding to 21043001 its reverse (10034012), we get a palindrome (31077013).

The spelling of 21043001 in words is "twenty-one million, forty-three thousand, one".