21269921 has 2 divisors, whose sum is σ = 21269922. Its totient is φ = 21269920.

The previous prime is 21269909. The next prime is 21269923. The reversal of 21269921 is 12996212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14167696 + 7102225 = 3764^2 + 2665^2 .

It is a cyclic number.

It is not a de Polignac number, because 21269921 - 2¹⁴ = 21253537 is a prime.

Together with 21269923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21269923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10634960 + 10634961.

It is an arithmetic number, because the mean of its divisors is an integer number (10634961).

Almost surely, 2^21269921 is an apocalyptic number.

It is an amenable number.

21269921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21269921 is an equidigital number, since it uses as much as digits as its factorization.

21269921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 32.

The square root of 21269921 is about 4611.9324583086. The cubic root of 21269921 is about 277.0694391636.

The spelling of 21269921 in words is "twenty-one million, two hundred sixty-nine thousand, nine hundred twenty-one".