21404021 has 8 divisors (see below), whose sum is σ = 21945504. Its totient is φ = 20869200.

The previous prime is 21404017. The next prime is 21404029. The reversal of 21404021 is 12040412.

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 21404021 - 2² = 21404017 is a prime.

It is a super-2 number, since 2×21404021² = 916264229936882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21403987 and 21404005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404029) 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 7 ways as a sum of consecutive naturals, for example, 5186 + ... + 8348.

It is an arithmetic number, because the mean of its divisors is an integer number (2743188).

Almost surely, 2^21404021 is an apocalyptic number.

It is an amenable number.

21404021 is a deficient number, since it is larger than the sum of its proper divisors (541483).

21404021 is a wasteful number, since it uses less digits than its factorization.

21404021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3331.

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21404021 is about 4626.4479895488. The cubic root of 21404021 is about 277.6504975932.

Adding to 21404021 its reverse (12040412), we get a palindrome (33444433).

The spelling of 21404021 in words is "twenty-one million, four hundred four thousand, twenty-one".