21041521 has 2 divisors, whose sum is σ = 21041522. Its totient is φ = 21041520.

The previous prime is 21041519. The next prime is 21041533. The reversal of 21041521 is 12514012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20295025 + 746496 = 4505^2 + 864^2 .

It is a cyclic number.

It is not a de Polignac number, because 21041521 - 2¹ = 21041519 is a prime.

Together with 21041519, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21041495 and 21041504.

It is not a weakly prime, because it can be changed into another prime (21041221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10520760 + 10520761.

It is an arithmetic number, because the mean of its divisors is an integer number (10520761).

Almost surely, 2^21041521 is an apocalyptic number.

It is an amenable number.

21041521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21041521 is an equidigital number, since it uses as much as digits as its factorization.

21041521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21041521 is about 4587.1037703544. The cubic root of 21041521 is about 276.0741285519.

Adding to 21041521 its reverse (12514012), we get a palindrome (33555533).

The spelling of 21041521 in words is "twenty-one million, forty-one thousand, five hundred twenty-one".