21100421 has 4 divisors (see below), whose sum is σ = 21151200. Its totient is φ = 21049644.

The previous prime is 21100411. The next prime is 21100423. The reversal of 21100421 is 12400112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21100421 - 2⁶ = 21100357 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 (21100423) 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 3 ways as a sum of consecutive naturals, for example, 24761 + ... + 25598.

It is an arithmetic number, because the mean of its divisors is an integer number (5287800).

Almost surely, 2^21100421 is an apocalyptic number.

It is an amenable number.

21100421 is a deficient number, since it is larger than the sum of its proper divisors (50779).

21100421 is an equidigital number, since it uses as much as digits as its factorization.

21100421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50778.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 21100421 is about 4593.5194568000. The cubic root of 21100421 is about 276.3314866455.

Adding to 21100421 its reverse (12400112), we get a palindrome (33500533).

The spelling of 21100421 in words is "twenty-one million, one hundred thousand, four hundred twenty-one".