21434921 has 2 divisors, whose sum is σ = 21434922. Its totient is φ = 21434920.

The previous prime is 21434911. The next prime is 21434939. The reversal of 21434921 is 12943412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13249600 + 8185321 = 3640^2 + 2861^2 .

It is a cyclic number.

It is not a de Polignac number, because 21434921 - 2¹⁰ = 21433897 is a prime.

It is a Sophie Germain prime.

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

It is a Curzon number.

It is a zygodrome in base 3.

It is not a weakly prime, because it can be changed into another prime (21434911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10717460 + 10717461.

It is an arithmetic number, because the mean of its divisors is an integer number (10717461).

Almost surely, 2^21434921 is an apocalyptic number.

It is an amenable number.

21434921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21434921 is an equidigital number, since it uses as much as digits as its factorization.

21434921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 26.

The square root of 21434921 is about 4629.7862801646. The cubic root of 21434921 is about 277.7840437638.

The spelling of 21434921 in words is "twenty-one million, four hundred thirty-four thousand, nine hundred twenty-one".