21409643 has 8 divisors (see below), whose sum is σ = 22056720. Its totient is φ = 20766240.

The previous prime is 21409631. The next prime is 21409669. The reversal of 21409643 is 34690412.

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 21409643 - 2¹⁸ = 21147499 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21409603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14813 + ... + 16193.

It is an arithmetic number, because the mean of its divisors is an integer number (2757090).

Almost surely, 2^21409643 is an apocalyptic number.

21409643 is a deficient number, since it is larger than the sum of its proper divisors (647077).

21409643 is a wasteful number, since it uses less digits than its factorization.

21409643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1837.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 21409643 is about 4627.0555432154. The cubic root of 21409643 is about 277.6748047775.

The spelling of 21409643 in words is "twenty-one million, four hundred nine thousand, six hundred forty-three".