20553521 has 2 divisors, whose sum is σ = 20553522. Its totient is φ = 20553520.

The previous prime is 20553517. The next prime is 20553529. The reversal of 20553521 is 12535502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16289296 + 4264225 = 4036^2 + 2065^2 .

It is a cyclic number.

It is not a de Polignac number, because 20553521 - 2² = 20553517 is a prime.

It is a super-3 number, since 3×20553521³ (a number of 23 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20553529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10276760 + 10276761.

It is an arithmetic number, because the mean of its divisors is an integer number (10276761).

Almost surely, 2^20553521 is an apocalyptic number.

It is an amenable number.

20553521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20553521 is an equidigital number, since it uses as much as digits as its factorization.

20553521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 20553521 is about 4533.5991221104. The cubic root of 20553521 is about 273.9231540763.

The spelling of 20553521 in words is "twenty million, five hundred fifty-three thousand, five hundred twenty-one".