21404431 has 8 divisors (see below), whose sum is σ = 22590720. Its totient is φ = 20224152.

The previous prime is 21404417. The next prime is 21404437. The reversal of 21404431 is 13440412.

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 21404431 - 2⁵ = 21404399 is a prime.

It is a super-2 number, since 2×21404431² = 916299332867522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21404399 and 21404408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404437) 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, 7146 + ... + 9688.

It is an arithmetic number, because the mean of its divisors is an integer number (2823840).

Almost surely, 2^21404431 is an apocalyptic number.

21404431 is a deficient number, since it is larger than the sum of its proper divisors (1186289).

21404431 is a wasteful number, since it uses less digits than its factorization.

21404431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3005.

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 21404431 is about 4626.4922997883. The cubic root of 21404431 is about 277.6522704062.

Adding to 21404431 its reverse (13440412), we get a palindrome (34844843).

The spelling of 21404431 in words is "twenty-one million, four hundred four thousand, four hundred thirty-one".