21412921 has 4 divisors (see below), whose sum is σ = 21670992. Its totient is φ = 21154852.

The previous prime is 21412889. The next prime is 21412949. The reversal of 21412921 is 12921412.

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 21412921 - 2⁵ = 21412889 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21412892 and 21412901.

It is not an unprimeable number, because it can be changed into a prime (21412021) 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, 128911 + ... + 129076.

It is an arithmetic number, because the mean of its divisors is an integer number (5417748).

Almost surely, 2^21412921 is an apocalyptic number.

It is an amenable number.

21412921 is a deficient number, since it is larger than the sum of its proper divisors (258071).

21412921 is an equidigital number, since it uses as much as digits as its factorization.

21412921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 258070.

The product of its digits is 288, while the sum is 22.

The square root of 21412921 is about 4627.4097506056. The cubic root of 21412921 is about 277.6889755192.

The spelling of 21412921 in words is "twenty-one million, four hundred twelve thousand, nine hundred twenty-one".