21430821 has 8 divisors (see below), whose sum is σ = 29001184. Its totient is φ = 14073840.

The previous prime is 21430793. The next prime is 21430831. The reversal of 21430821 is 12803412.

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

It is not a de Polignac number, because 21430821 - 2⁶ = 21430757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21430831) 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, 53110 + ... + 53511.

It is an arithmetic number, because the mean of its divisors is an integer number (3625148).

Almost surely, 2^21430821 is an apocalyptic number.

It is an amenable number.

21430821 is a deficient number, since it is larger than the sum of its proper divisors (7570363).

21430821 is a wasteful number, since it uses less digits than its factorization.

21430821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106691.

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21430821 is about 4629.3434739712. The cubic root of 21430821 is about 277.7663314335.

The spelling of 21430821 in words is "twenty-one million, four hundred thirty thousand, eight hundred twenty-one".