20001521 has 2 divisors, whose sum is σ = 20001522. Its totient is φ = 20001520.

The previous prime is 20001517. The next prime is 20001551. The reversal of 20001521 is 12510002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14145121 + 5856400 = 3761^2 + 2420^2 .

It is a cyclic number.

It is not a de Polignac number, because 20001521 - 2² = 20001517 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20001551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10000760 + 10000761.

It is an arithmetic number, because the mean of its divisors is an integer number (10000761).

Almost surely, 2^20001521 is an apocalyptic number.

It is an amenable number.

20001521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20001521 is an equidigital number, since it uses as much as digits as its factorization.

20001521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 20001521 is about 4472.3060047363. The cubic root of 20001521 is about 271.4486425337.

Adding to 20001521 its reverse (12510002), we get a palindrome (32511523).

The spelling of 20001521 in words is "twenty million, one thousand, five hundred twenty-one".