21232421 has 8 divisors (see below), whose sum is σ = 24306624. Its totient is φ = 18168480.

The previous prime is 21232399. The next prime is 21232429. The reversal of 21232421 is 12423212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21232421 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21232421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21232429) 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, 2561 + ... + 7001.

It is an arithmetic number, because the mean of its divisors is an integer number (3038328).

Almost surely, 2^21232421 is an apocalyptic number.

It is an amenable number.

21232421 is a deficient number, since it is larger than the sum of its proper divisors (3074203).

21232421 is an equidigital number, since it uses as much as digits as its factorization.

21232421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5131.

The product of its digits is 192, while the sum is 17.

The square root of 21232421 is about 4607.8651238941. The cubic root of 21232421 is about 276.9065140003.

Adding to 21232421 its reverse (12423212), we get a palindrome (33655633).

The spelling of 21232421 in words is "twenty-one million, two hundred thirty-two thousand, four hundred twenty-one".