21264521 has 2 divisors, whose sum is σ = 21264522. Its totient is φ = 21264520.

The previous prime is 21264497. The next prime is 21264541. The reversal of 21264521 is 12546212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19404025 + 1860496 = 4405^2 + 1364^2 .

It is a cyclic number.

It is not a de Polignac number, because 21264521 - 2¹⁰ = 21263497 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a plaindrome in base 16.

It is not a weakly prime, because it can be changed into another prime (21264541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10632260 + 10632261.

It is an arithmetic number, because the mean of its divisors is an integer number (10632261).

Almost surely, 2^21264521 is an apocalyptic number.

It is an amenable number.

21264521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21264521 is an equidigital number, since it uses as much as digits as its factorization.

21264521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 23.

The square root of 21264521 is about 4611.3469832577. The cubic root of 21264521 is about 277.0459897487.

The spelling of 21264521 in words is "twenty-one million, two hundred sixty-four thousand, five hundred twenty-one".